JP6060688B2 - Transfer device, communication system, and roundabout path detection method - Google Patents

Description

  The present invention relates to a transfer device, a communication system, and a roundabout path detection method.

  2. Description of the Related Art Conventionally, a technique for communicating with a terminal device via a network and providing a service is known. As an example of such a technique, a communication system is known in which information processing apparatuses that provide services are arranged at a plurality of bases, and the information processing apparatuses at each base are linked to provide services.

  For example, the communication system has a subnet in which LANs (Local Area Networks) of respective bases each having a gateway are connected by a switch. Then, the information processing apparatus at each site performs packet communication with a terminal apparatus outside the subnet via IP (Internet Protocol) via a gateway, and provides various services to the terminal apparatus.

  Here, one network address is assigned to the entire subnet. Also, the subnet notifies the terminal device of the gateway address of each LAN as a gateway for accessing the subnet. When the terminal device accesses the subnet, the terminal device selects one address from the notified gateway addresses, and transmits a packet with the selected address as a destination.

  However, the subnet notifies the terminal device of the address of the gateway for accessing the subnet, but does not notify information indicating in which LAN each information processing apparatus is installed. For this reason, the terminal apparatus may transmit the packet to a gateway of a LAN different from the LAN in which the information processing apparatus that is the transmission destination of the packet is arranged.

  Here, when a packet is transmitted to a gateway of a LAN different from the LAN in which the information processing apparatus that is the packet transmission destination is arranged, the information processing apparatus that is the packet transmission destination is arranged in the switch in the subnet. Transfer the packet to the LAN. As a result, packet communication is performed through a detour communication path without going through a LAN gateway in which an information processing apparatus as a packet transmission destination is arranged.

  In order to prevent packet communication via such a roundabout communication path, the management server that manages the LAN gateway in which each information processing apparatus is installed is configured so that the LAN gateway in which the information processing apparatus as a packet transmission destination is installed. A technique for notifying is known. For example, the management server stores the address of the information processing apparatus installed in each LAN and the address of the gateway in association with each other. When the management server receives the gateway inquiry and the information processing apparatus address, the management server notifies the inquiry source of the gateway address to be stored in association with the received information processing apparatus address. Prevent packet communication via

JP 2010-098555 A

“Cisco Mobility Locator / ID Separation Protocol for VM Mobility”, [online], [Search December 7, 2012], Internet <http://www.cisco.com/web/JP/product/hs/ios/iprs /ipr/prodlit/pdf/at_a_glance_c45-646350.pdf>

  However, the above-described technology for preventing packet communication via a detour communication path has a problem in that the processing cost for managing the addresses of all information processing apparatuses and gateways included in the subnet is high.

  In one aspect, an object is to shorten a communication path of a roundabout packet communication.

  In one aspect, the transfer device transmits and receives frames to and from a transfer device of a unit network having a gateway. In addition, the transfer device is a packet related to communication between an internal device installed in the network and an external device installed outside the network based on the destination address or source address of the packet in the frame to be transmitted / received It is determined whether or not. If the transfer device determines that the packet is a packet related to communication between the internal device and the external device, the transfer device notifies the external device of a gateway switching instruction.

  According to one aspect, it is possible to shorten the communication path of the roundabout packet communication.

FIG. 1 is a diagram illustrating the communication system according to the first embodiment. FIG. 2 is a schematic diagram illustrating an example of an IP address and a network address set for each device according to the first embodiment. FIG. 3 is a diagram illustrating an example of a functional configuration of the terminal device. FIG. 4A is a diagram illustrating an example of a routing table. FIG. 4B is a diagram illustrating an example of the ARP cache table of the terminal device. FIG. 5 is a diagram for explaining an example of an IP packet format. FIG. 6 is a diagram for explaining an example of the format of a roundabout notification message. FIG. 7 is a diagram for explaining an example of the updated routing table. FIG. 8 is a diagram for explaining an example of the functional configuration of the gateway on the subnet side. FIG. 9A is a diagram illustrating an example of the ARP cache table of the gateway. FIG. 9B is a diagram for explaining an example of an Ethernet frame format. FIG. 10A is a diagram illustrating an example of the format of an ARP request. FIG. 10B is a diagram illustrating an example of the format of an ARP response. FIG. 11 is a diagram illustrating an example of a functional configuration of the transfer device. FIG. 12 is a diagram illustrating an example of interface information. FIG. 13 is a diagram illustrating an example of the MAC learning table included in the transfer device. FIG. 14 is a diagram illustrating an example of roundabout packet identification information stored in the transfer device. FIG. 15 is a flowchart for explaining the flow of a roundabout packet determination process. FIG. 16 is a diagram for explaining a first variation of the interface information. FIG. 17 is a diagram illustrating variations in the format of the roundabout notification message. FIG. 18 is a diagram for explaining a variation of the updated routing table. FIG. 19 is a diagram for explaining a second variation of the interface information. FIG. 20 is a flowchart for explaining a variation of the roundabout packet determination process. FIG. 21 is a diagram for explaining a variation of the communication system. FIG. 22 is a schematic diagram illustrating a communication system according to a third embodiment. FIG. 23 is a schematic diagram illustrating an example of a functional configuration of a gateway according to the third embodiment. FIG. 24 is a schematic diagram illustrating an example of an address correspondence table stored in the gateway according to the third embodiment. FIG. 25 is a schematic diagram illustrating an example of the format of a roundabout notification message according to the third embodiment. FIG. 26 is a schematic diagram illustrating an example of a functional configuration of the transfer apparatus according to the third embodiment. FIG. 27 is a schematic diagram illustrating an example of roundabout packet identification information stored in the transfer apparatus according to the third embodiment. FIG. 28 is a flowchart for explaining the flow of the roundabout packet determination process according to the third embodiment. FIG. 29 is a diagram for explaining a variation of the functional configuration of the gateway. FIG. 30 is a diagram for explaining a variation of the ARP cache table stored in the gateway. FIG. 31 is a schematic diagram illustrating a communication system according to a fifth embodiment. FIG. 32 is a schematic diagram illustrating an example of a functional configuration of the transfer apparatus according to the fifth embodiment. FIG. 33 is a schematic diagram illustrating an example of interface information according to the fifth embodiment. FIG. 34 is a flowchart for explaining the flow of a roundabout packet determination process according to the fifth embodiment. FIG. 35 is a diagram for explaining variations of the interface information according to the sixth embodiment. FIG. 36 is a schematic diagram illustrating variations of roundabout packet identification information according to the sixth embodiment. FIG. 37 is a diagram for explaining a variation of the functional configuration of the transfer apparatus according to the sixth embodiment. FIG. 38 is a diagram for explaining an example of the MAC address list of the gateway. FIG. 39 is a diagram for explaining variations of roundabout packet identification information when a roundabout packet is determined using an ARP response. FIG. 40 is a diagram for describing an example of a computer that executes a determination program.

  Hereinafter, embodiments of a transfer device, a communication system, and a roundabout path detection method according to the present application will be described in detail with reference to the accompanying drawings. The disclosed technology is not limited by this embodiment. In addition, the embodiments may be combined as appropriate within a consistent range.

  In the following first embodiment, an example of a communication system will be described with reference to FIG. FIG. 1 is a diagram illustrating the communication system according to the first embodiment. In the example illustrated in FIG. 1, the communication system 1 includes a terminal device 2, a network 3, a first base 4, and a second base 5. The first base 4 has a LAN (Local Area Network) 11a, and the second base 5 has a LAN 11b. The first base 4 and the second base 5 are, for example, data centers that are respectively arranged in different regions.

  The LAN 11a includes a gateway 20a, a transfer device 30a, and a server 40a. The LAN 11b includes a gateway 20b, a transfer device 30b, and a server 40b. The LAN 11a and the LAN 11b are connected via the transfer device 30a and the transfer device 30b, and operate as the subnet 10 to which one network address is assigned as a whole.

  Here, the transfer device 30a has a plurality of interfaces (IF), and is connected to the gateway 20a, the server 40a, and the transfer device 30b via each interface. Similarly to the transfer device 30a, the transfer device 30b has a plurality of interfaces, and is connected to the gateway 20b, the server 40b, and the transfer device 30a via each interface.

  In FIG. 1, for easy understanding, the subnet 10 in which two bases are linked is described. However, the embodiment is not limited to this, and the subnet 10 is installed in three or more bases. A connected LAN may be connected. Further, in the example shown in FIG. 1, an example in which each LAN 11a and 11b has one server is described. However, the embodiment is not limited to this, and each LAN 11a and 11b includes two or more servers. You may have.

  Here, an IP address and a network address used for packet communication are assigned to the terminal device 2, the gateways 20a and 20b, the subnet 10, and the servers 40a and 40b. Hereinafter, an example of an IP address assigned to the terminal device 2 and the gateways 20a and 20b and a network address assigned to the subnet 10 and the servers 40a and 40b will be described with reference to FIG.

  FIG. 2 is a schematic diagram illustrating an example of an IP address and a network address set for each device according to the first embodiment. In the example illustrated in FIG. 2, the terminal device 2 is assigned the IP address “10.0.0.1”, the gateway 20 a is assigned “10.0.1.1”, and the gateway 20 b is assigned “ 10.0.2.2 "is assigned. Therefore, “10.0.1.1” and “10.0.2.2” are notified to the terminal device 2 as gateway addresses when accessing the subnet 10.

  The subnet 10 is assigned a network address and a mask value “192.168.0.0/24”. The server 40a is assigned the network address “192.168.0.1” in the subnet 10, and the server 40b is assigned the network address “192.168.0.2” in the subnet 10. Yes.

  The server 40b is assigned a MAC (Media Access Control address) address “M1”, and the MAC address “M2” is assigned to the interface on the subnet 10 side of the gateway 20a. Further, the MAC address “M3” is assigned to the server 40a, and the MAC address “M4” is assigned to the interface on the subnet 10 side of the gateway 20b.

  Next, functions of the terminal device 2, the network 3, the gateway 20a, the transfer device 30a, and the server 40a of the communication system 1 will be described. The gateway 20b performs the same function as the gateway 20a, the transfer device 30b performs the same function as the transfer device 30a, and the server 40b performs the same function as the server 40a. Description is omitted.

  The terminal device 2 is a terminal device that receives provision of various services from the subnet 10, and is, for example, an information processing device such as a PC (Personal Computer), a PDA (Personal Digital Assistant), or a mobile terminal device. Specifically, the terminal device 2 is notified of the IP addresses of the gateways 20 a and 20 b included in the subnet 10. As a result, the terminal device 2 selects either the gateway 20a or the gateway 20b as a priority gateway. When the terminal device 2 performs packet communication with the servers 40 a and 40 b included in the subnet 10, the terminal device 2 transmits an IP packet via the network 3 with the selected priority gateway as a destination.

  For example, the terminal device 2 stores a routing table in which the network address of the subnet 10 is associated with the IP address of the gateway 20a and the IP address of the gateway 20b. When the terminal device 2 transmits an IP packet to the server 40a, the terminal device 2 generates an IP packet in which the destination IP address “192.168.0.1” is stored in the IP header. Further, the terminal device 2 determines that the destination IP address “192.168.0.1” is included in the network address of the subnet 10, and identifies the gateways 20 a and 20 b of the subnet 10.

  Next, when the gateway 20a is selected as the priority gateway, the terminal device 2 acquires the MAC address of the gateway 20a using the IP address “10.0.1.1” of the gateway 20a. Then, the terminal device 2 generates a frame (Ethernet frame) having the acquired MAC address as the destination MAC address, and stores the generated IP packet in the generated frame. Thereafter, the terminal device 2 transmits a frame storing the IP packet.

  The network 3 is a public network such as the Internet or a closed network such as a LAN. For example, the network 3 performs packet transfer according to the destination IP address of the packet in the frame received from the terminal device 2.

  The gateway 20a is connected to the network 3 and the IF (Interface) of the transfer device 30a, and relays communication between the servers 40a and 40b of the subnet 10 and the terminal device 2. Specifically, when the gateway 20a receives a frame transmitted by the terminal device 2 via the network 3, the gateway 20a extracts an IP packet in the received frame. Then, the gateway 20a transfers the packet according to the destination IP address in the extracted IP packet. In the following description, an IP packet in a frame received by the gateway 20a may be described as a packet received by the gateway 20a.

  For example, the gateway 20a stores an ARP (Address Resolution Protocol) table in which the IP address “192.168.0.1” of the server 40a is associated with the MAC address “M3”. When the gateway 20a receives an IP packet whose destination IP address is “192.168.0.1”, the gateway 20a receives the MAC address “192.168.0.1” associated with “192.168.0.1” in the ARP table. M3 "is acquired. Then, the gateway 20a stores the received IP packet in a frame having the acquired MAC address “M3” of the server 40a as the destination MAC address, and transmits the frame to the transfer device 30a.

  On the other hand, when the gateway 20a receives an IP packet whose destination IP address is the IP address “192.168.0.2” of the server 40b, the gateway 20a determines that the MAC address corresponding to the ARP table is not stored. . In such a case, the gateway 20a broadcasts an ARP request with the IP address “192.168.0.2” as a target address to the subnet 10 in order to acquire the MAC address of the server 40b. Specifically, the gateway 20a broadcasts a frame storing an ARP request packet.

  In such a case, the ARP request is transferred to the server 40b via the transfer device 30a and the transfer device 30b. As a result, the server 40b generates an ARP response storing the MAC address “M1” of the server 40b, and transmits the generated ARP response to the gateway 20a via the transfer device 30b and the transfer device 30a. In such a case, the gateway 20a stores the IP packet received from the terminal device 2 in the frame having the MAC address of the server 40b stored in the ARP response as the destination MAC address, and transmits the frame to the transfer device 30a. To do.

  The transfer device 30a is a transfer device that relays frame communication between the LAN 11a and the LAN 11b, and is, for example, an L3 switch. A detailed example will be described. The transfer device 30a stores an FDB (Forwarding DataBase) in which a destination MAC address is associated with an interface that transmits a frame. When the transfer device 30a receives the frame from the gateway 20a, the server 40a, or the transfer device 30b, the transfer device 30a acquires the destination MAC address of the received frame and outputs the frame from the interface associated with the acquired destination MAC address.

  For example, when the transfer device 30a receives a packet with the destination MAC address “M1” from the server 40a, the transfer device 30a transmits the received frame to the transfer device 30b. Then, the transfer device 30b transmits the frame received from the transfer device 30a to the server 40b.

  The server 40a is a server that provides various services to the terminal device 2 by performing packet communication with the terminal device 2, and is, for example, an information processing device that executes a program for providing various services. Further, the server 40a communicates with the server 40b to exchange data, and provides various services to the terminal device 2 in cooperation with the server 40b.

  Here, although the IP address of each gateway 20a, 20b is notified to the terminal device 2, it is not notified to which of the LANs 11a, 11b each server 40a, 40b is included. For this reason, when the gateway device 20a is selected as the priority gateway, the terminal device 2 transmits a frame addressed to the server 40b to the gateway 20a even though the gateway 20b is installed in the LAN 11b having the server 40b. There is a case.

  In such a case, since the packet received by the gateway 20a is transferred to the server 40b via the transfer device 30a and the transfer device 30b, the communication route between the terminal device 2 and the server 40b is a detour route, that is, a detour. It becomes a route. The roundabout path is a path for packet communication performed via a gateway different from the gateway installed in the packet transmission destination LAN.

  Therefore, in the communication system 1, the transfer device 30a that relays communication between the LAN 11a and the LAN 11b determines whether the communication path is a roundabout path. Hereinafter, a process in which the transfer device 30a determines whether the communication path is a roundabout path will be described.

  First, the transfer device 30a stores interface information indicating whether the connection destination of each interface is a LAN other than the LAN 11a. When the frame is received, the transfer device 30a determines whether or not the interface that sends out the received frame is connected to a LAN other than the LAN 11a, that is, the transfer device 30b of the LAN 11b.

  In addition, when an interface for sending a frame is connected to the transfer device 30b, the transfer device 30a determines whether the type of the packet in the frame to be sent is an IP packet used for data communication or the like. . Here, in the IP packet, the IP address of the device that transmitted the IP packet is stored as the source IP address, and the IP address of the device that is the destination of the IP packet is stored as the destination IP address. For example, in the IP packet transmitted from the terminal device 2 to the server 40b, the IP address of the transfer device 2 is stored as the transmission source IP address, and the IP address of the server 40b is stored as the destination IP address.

  Then, when the packet type in the frame to be transmitted is an IP packet, the transfer device 30a determines whether or not the transmission source IP address stored in the IP packet is within the range of the IP address of the subnet 10. judge. That is, the transfer device 30a determines whether or not the IP packet to be transmitted is an IP packet related to packet communication between the servers 40a and 40b that are internal devices of the subnet 10 and the terminal device 2 that is an external device of the subnet 10. To do.

  Thereafter, when the transfer device 30a determines that the source IP address of the IP packet is not within the range of the IP address of the subnet 10, the packet in the received frame is a roundabout packet transmitted / received via the roundabout path. Is determined. When the transfer device 30a determines that the received packet is a roundabout packet, the transfer device 30a transmits a notification instructing the terminal device 2 to switch the gateway via the gateway 20a.

  That is, in the example shown in FIG. 1, each of the LANs 11a and 11b has a gateway. Here, when the IP packet transmitted / received between the server 40a and the terminal device 2 is transferred from the LAN 11a to the LAN 11b, the transfer device 30a can determine that the transferred IP packet is a roundabout packet. For this reason, when the transmission source IP address of the IP packet in the frame transmitted to the transmission device 30b is not the IP address of the subnet 10, for example, when the transmission source is the terminal device 2, the transfer device 30a transmits the IP to be transmitted. It is determined that the packet is a roundabout packet.

  If the transfer device 30a determines that the IP packet in the frame to be transmitted is a roundabout packet, the transfer device 30a notifies the terminal device 2 of the gateway switching. As a result, the terminal device 2 rewrites the routing table and switches the priority gateway from the gateway 20a to the gateway 20b. For this reason, the transfer device 30a can prevent the communication path from being a roundabout path without managing the LAN in which the servers 40a and 40b of the subnet 10 are installed. The transfer device 30b may determine whether or not the communication path between the terminal device 2 and the server 40a is via a roundabout path by performing the same processing as that of the transfer apparatus 30a.

  Next, an example of a functional configuration of the terminal device 2, the gateway 20a, and the transfer device 30a will be described with reference to the drawings. First, an example of a functional configuration of the terminal device 2 will be described with reference to FIG.

  FIG. 3 is a diagram illustrating an example of a functional configuration of the terminal device. In the example shown in FIG. 3, the terminal device 2 has a routing table 12a and an ARP cache table 12b. The terminal device 2 includes a data generation unit 13, a transfer processing unit 14, a transmission / reception unit 15, an interface 16, a message identification unit 17, a data processing unit 18, and a routing table update unit 19.

  The routing table 12a stores an IP address of a gateway included in a network that is a packet transmission destination. For example, FIG. 4A is a diagram illustrating an example of a routing table. As shown in FIG. 4A, the routing table 12a stores a destination IP address, a gateway IP address, and a communication cost in association with each other.

  Here, the destination IP address is an IP address and a mask value assigned to a network that is a packet transmission destination. The gateway IP address is an IP address assigned to the gateway of the network to which the associated destination IP address is assigned. The communication cost is a value of communication cost generated when packet communication is performed via the gateway indicated by the associated IP address, and is a value calculated from a network delay, a line bandwidth, and the like.

  For example, the routing table 12a corresponds to the network address of the subnet 10, the mask value “192.168.0.0/24”, the IP address “10.0.2.2” of the gateway 20b, and the communication cost “20”. Add and remember. Further, the routing table 12a corresponds to the network address of the subnet 10, the mask value “192.168.0.0/24”, the IP address “10.0.1.1” of the gateway 20a, and the communication cost “10”. Add and remember. As a result, the terminal device 2 selects the gateway 20a having a low communication cost as the priority gateway.

  Returning to FIG. 3, the ARP cache table 12b stores a destination IP address when a packet is transmitted to each of the gateways 20a and 20b and a destination MAC address stored in the frame in association with each other. For example, FIG. 4B is a diagram illustrating an example of the ARP cache table of the terminal device. In the example shown in FIG. 4B, the ARP cache table 12b stores the IP address “10.0.1.1” of the gateway 20a and the MAC address “M11” on the network 3 side of the gateway 20a in association with each other. The ARP cache table 12b stores the IP address “10.0.2.2” of the gateway 20b and the MAC address “M12” on the network 3 side of the gateway 20b in association with each other.

  Returning to FIG. 3, the data generation unit 13 generates data to be transmitted to the servers 40 a and 40 b included in the subnet 10, and outputs the generated data and the IP address indicating the transmission destination to the transfer processing unit 14. For example, when the data generation unit 13 generates data to be transmitted to the server 40 b, the data generation unit 13 outputs the data and the IP address “192.168.0.2” of the server 40 b to the transfer processing unit 14.

  When the transfer processing unit 14 receives the data and the IP address indicating the data transmission destination from the data generation unit 13, the transfer processing unit 14 collates the received IP address with the routing table 12a, and the IP address of the gateway included in the network that is the data transmission destination. Get the address. Specifically, the transfer processing unit 14 selects an entry having the largest value of the network mask among the destination IP addresses including the IP address indicating the data transmission destination.

  Here, when a plurality of entries are selected, the transfer processing unit 14 selects an entry having the lowest communication cost value among the selected entries. Then, the transfer processing unit 14 acquires the IP address of the gateway stored in the selected entry. For example, when the routing table 12a stores the information illustrated in FIG. 4A, the transfer processing unit 14 has the same mask value for each entry, and therefore the IP address of the gateway 20a having the lowest communication cost value. The address “10.0.1.1” is acquired.

  Thereafter, the transfer processing unit 14 transmits an IP packet using the acquired IP address of the gateway. Specifically, the transfer processing unit 14 sets the IP address “192.168.0.2” received from the data generation unit 13 as the destination IP address, and stores the data received from the data generation unit 13 in the payload of the IP packet. An IP packet is generated. Also, the transfer processing unit 14 generates a frame having the MAC address “M11” associated with the IP address “10.0.1.1” of the gateway 20a as the destination MAC address from the ARP cache table 12b. Then, the transfer processing unit 14 stores the generated IP packet in the generated frame, and outputs the frame to the transmission / reception unit 15.

  Here, FIG. 5 is a diagram for explaining an example of the format of the IP packet. FIG. 5 shows an example of the field name of the IP packet and the value stored in each field. For example, the transfer processing unit 14 stores the IP address “10.0.0.1” of the terminal device 2 as the source IP address, and the IP address “192.168.0.2” of the server 40b as the destination IP address. Is generated in the header part.

  Then, the transfer processing unit 14 stores the data received from the data generation unit 13 in the payload of the generated IP packet. Further, the transfer processing unit 14 adds the Ethernet header having the MAC address “M11” of the interface on the network 3 side of the gateway 20a to the destination MAC address to the IP packet shown in FIG. Store. Then, the transfer processing unit 14 outputs the frame storing the IP packet to the transmission / reception unit 15.

  Returning to FIG. 3, the transmission / reception unit 15 transmits / receives a frame via the interface 16. For example, when the transmission / reception unit 15 receives a frame from the transfer processing unit 14, the transmission / reception unit 15 transmits the frame to the network 3 via the interface 16. In addition, when the transmission / reception unit 15 receives a frame via the interface 16, the transmission / reception unit 15 outputs the received frame to the message identification unit 17. The interface 16 is an interface that transmits and receives a frame in which a packet is stored. For example, the interface 16 is a communication port that the terminal device 2 has.

  When the packet in the frame received from the transmission / reception unit 15 is a roundabout notification message, the message identification unit 17 outputs the received roundabout notification message to the routing table update unit 19. In addition, when the packet in the received frame is an IP packet related to packet communication, the message identification unit 17 extracts the packet from the frame and outputs the extracted packet to the data processing unit 18.

  When receiving the IP packet from the message identification unit 17, the data processing unit 18 acquires the data stored in the payload of the received IP packet, and executes various processes using the acquired data. Further, when receiving the roundabout notification message from the message identifying unit 17, the routing table updating unit 19 updates the routing table 12a based on the received roundabout notification message, and switches the gateway.

  For example, FIG. 6 is a diagram illustrating an example of the format of a roundabout notification message. As shown in FIG. 6, the data processing unit 18 receives a packet in which a transmission source IP address, a destination IP address, and a roundabout flag are stored as a roundabout notification message. Here, the source IP address and destination IP address shown in FIG. 6 are not the IP address indicating the source or destination of the roundabout notification message, but the source and destination of the IP packet transferred via the roundabout path. IP address shown. The roundabout flag is information indicating whether an IP packet destined for the IP address stored as the destination IP address is a roundabout packet.

  For example, in the example illustrated in FIG. 6, the routing table update unit 19 performs a roundabout with a source IP address “10.0.0.1”, a destination IP address “192.168.0.2”, and a roundabout flag “ON”. Receive notification messages. In such a case, the routing table update unit 19 switches the gateway when transmitting a packet having “192.168.0.2” as the destination IP address.

  FIG. 7 is a diagram for explaining an example of the updated routing table. As illustrated in FIG. 7, the routing table update unit 19 adds an entry storing the destination IP address “192.168.0.2” of the roundabout notification message to the destination IP address. Also, the routing table update unit 19 sets, for example, “/ 32” as a mask value having a larger value than other entries.

  In addition, the routing table update unit 19 stores the IP address “10.0.2.2” of the gateway 20b that is not the priority gateway in the added entry. Also, the routing table update unit 19 stores the communication cost “20” associated with the IP address “10.0.2.2” of the gateway 20b before the entry is added in the added entry. As a result, the transfer processing unit 14 selects the entry having the largest mask value of the destination IP address, and therefore selects the gateway 20b as the priority gateway when transmitting a packet destined for the server 40b.

  Next, the functional configuration of the gateway 20a will be described with reference to FIG. FIG. 8 is a diagram for explaining an example of the functional configuration of the gateway on the subnet side. In the example shown in FIG. 8, the gateway 20a includes interfaces 21, 28, transmission / reception units 22, 27, a message identification unit 23, a roundabout communication identification unit 24, a route change notification unit 25, a transfer processing unit 26, and an ARP cache table storage unit 29a. Have The interface 21 is an interface on the network 3 side, and is assigned the MAC address “M11”. The interface 28 is an interface on the subnet 10 side, and is assigned a MAC address M2.

  The ARP cache table storage unit 29a stores an IP address and a MAC address in association with each other. For example, FIG. 9A is a diagram illustrating an example of the ARP cache table of the gateway. In the example illustrated in FIG. 9A, the ARP cache table storage unit 29a stores an ARP cache table in which the IP address “192.168.0.1” and the MAC address “M3” are associated with each other. That is, the ARP cache table storage unit 29a stores the IP address and MAC address of the server 40a in association with each other.

  Returning to FIG. 8, when the transmission / reception unit 22 receives a frame from the network 3 via the interface 21, the transmission / reception unit 22 outputs the received frame to the message identification unit 23. When the roundabout notification message is received from the route change notification unit 25, the transmission / reception unit 22 outputs the received roundabout notification message to the network 3. Further, when the transmission / reception unit 22 receives a frame from the transfer processing unit 26, the transmission / reception unit 22 outputs the frame to the network 3 via the interface 21.

  When the message identification unit 23 receives a frame from the transmission / reception unit 22, the message identification unit 23 outputs the received frame to the transfer processing unit 26. In addition, when receiving a frame from the transmission / reception unit 27, the message identification unit 23 determines whether the packet in the received frame is an IP packet, a roundabout notification message packet, or an ARP response packet. To do. If the packet in the received frame is an IP packet or an ARP response packet, the message identification unit 23 outputs the packet to the transfer processing unit 26. On the other hand, when the packet in the received frame is a roundabout notification message packet, the message identifying unit 23 outputs the received roundabout notification message to the roundabout communication specifying unit 24.

  When the roundabout communication specifying unit 24 receives the roundabout notification message from the message identifying unit 23, the roundabout communication specifying unit 24 uses the source IP address of the received roundabout notification message to specify an external device that performs packet communication via the roundabout path. Then, the roundabout communication specifying unit 24 notifies the route change notification unit 25 of the roundabout notification message and the specified external device.

  When the route change notification unit 25 receives the roundabout notification message and the external device specified by the roundabout communication specification unit 24 from the roundabout communication specification unit 24, the packet whose destination is the external device specified by the roundabout communication specification unit 24 And a roundabout notification message is stored in the generated packet. Then, the route change notification unit 25 stores the roundabout notification message in a frame having the MAC address of the external device specified by the roundabout communication specifying unit 24 as the destination MAC address, and outputs the frame to the transmission / reception unit 22.

  The transfer processing unit 26 executes packet transfer processing of the gateway 20a. For example, when receiving a frame from the message identification unit 23, the transfer processing unit 26 identifies the destination IP address of the IP packet in the received frame. Then, when the identified destination IP address is not included in the network address “192.168.0.0/24” of the subnet 10, the transfer processing unit 26 acquires a MAC address corresponding to the destination IP address. Thereafter, the transfer processing unit 26 stores the IP packet in a frame having the acquired MAC address as the destination MAC address, and outputs the frame to the transmission / reception unit 22.

  In addition, when the identified destination IP address is included in the network address “192.168.0.0/24” of the subnet 10, the transfer processing unit 26 determines that the identified destination IP address is in the ARP cache table storage unit 29a. It is determined whether or not it is stored. In addition, when the identified destination IP address is stored in the ARP cache table storage unit 29a, the transfer processing unit 26 acquires a MAC address associated with the identified destination IP address. On the other hand, if the identified destination IP address is not stored in the ARP cache table storage unit 29a, the transfer processing unit 26 issues an ARP request and acquires the MAC address of the device indicated by the destination IP address. Then, the transfer processing unit 26 stores the IP packet received from the message identification unit 23 in a frame having the acquired MAC address as the destination MAC address. Thereafter, the transfer processing unit 26 outputs the frame to the transmission / reception unit 27.

  Here, an example of a format of a frame transferred within the subnet 10 will be described with reference to FIG. 9B. FIG. 9B is a diagram for explaining an example of an Ethernet frame format. As shown in FIG. 9B, the Ethernet frame has a destination MAC address, a source IP address, a destination IP address, and a payload. That is, the Ethernet frame has a format in which the destination MAC address is added to the IP packet.

  For example, when receiving the IP packet whose destination IP address is “192.168.0.1”, the transfer processing unit 26 receives the MAC associated with “192.168.0.1” from the ARP cache table storage unit 29a. The address “M3” is acquired. Then, the transfer processing unit 26 stores the IP address “10.0.0.1” of the gateway 20a in the source IP address, stores the IP packet in the frame having the destination MAC address “M3”, Is output to the transmission / reception unit 27.

  On the other hand, if the destination IP address is not stored in the ARP cache table storage unit 29a, the transfer processing unit 26 issues an ARP request. Hereinafter, the process in which the transfer processing unit 26 acquires the MAC address of the device indicated by the destination IP address using the ARP request will be described in detail with reference to FIGS. 10A and 10B. First, a process in which the transfer processing unit 26 issues an ARP request will be described with reference to FIG. 10A.

  FIG. 10A is a diagram illustrating an example of the format of an ARP request. As illustrated in FIG. 10A, the transfer processing unit 26 generates an ARP request in which a transmission source MAC address, a destination MAC address, a target address, and a payload are stored. Here, the transmission source MAC address is the MAC address of the transmission source of the ARP request, and the destination MAC address is the destination MAC address of the ARP request. The target address is an IP address indicating a device that requests notification of a MAC address.

  Since the transfer processing unit 26 broadcasts an ARP request, the transfer MAC unit stores “ff: ff: ff: ff: ff: ff”, which is a broadcast address, in the destination MAC address. Here, the various information of the ARP request shown in FIG. 10A is information stored in the packet of the ARP request and is different from the information used for transfer.

  For example, the transfer processing unit 26 receives a frame in which an IP packet having an IP address “192.168.0.2” as a destination IP address is stored. In such a case, the transfer processing unit 26 stores the MAC address “M2” of the gateway 20a as the transmission source MAC address in the ARP request. Further, the transfer processing unit 26 stores “ff: ff: ff: ff: ff: ff”, which is the broadcast address, as the destination MAC address in the ARP request, and “192.168.0.2” as the target address. Store. Then, the transfer processing unit 26 stores the generated ARP request in a frame and outputs the frame to the transmission / reception unit 27.

  Then, the transmission / reception unit 27 broadcasts the frame storing the ARP request to the subnet 10 via the interface 28. As a result, the server 40b whose IP address is “192.168.0.2” generates an ARP response notifying the MAC address. Specifically, the server 40b generates an ARP response in which the transmission source MAC address of the ARP request is the destination MAC address and the MAC address of the server 40b is stored in the transmission source MAC address. Then, the server 40b stores the ARP response in a frame whose destination MAC address is the MAC address of the gateway 20a, and outputs the frame to the transfer device 30b.

  FIG. 10B is a diagram illustrating an example of the format of an ARP response. As illustrated in FIG. 10B, the server 40b generates an ARP response including a transmission source MAC address, a destination MAC address, a transmission source protocol address, and a payload. For example, in the ARP response, the server 40b stores the MAC address “M1” of the server 40b as the source MAC address and stores the MAC address “M2” of the interface on the subnet 10 side of the gateway 20a as the destination MAC address. Further, the server 40b stores the IP address “192.168.0.2” of the server 40b as the source protocol address. Then, the server 40b stores the ARP response in a frame addressed to the gateway 20a, and transmits the frame in which the ARP response is stored to the gateway 20a via the transfer device 30b and the transfer device 30a.

  As a result, the transfer processing unit 26 acquires the MAC address of the server 40b from the transmission source MAC address of the ARP response. Further, the transfer processing unit 26 stores the IP packet received from the message identifying unit 23 in a frame with the MAC address of the server 40b as the destination MAC address. Then, the transfer processing unit 26 outputs the frame to the transmission / reception unit 27.

  When the transmission / reception unit 27 receives various frames from the transfer device 30 a via the interface 28, the transmission / reception unit 27 outputs the received various frames to the message identification unit 23. In addition, when the transmission / reception unit 27 receives a frame from the transfer processing unit 26, the transmission / reception unit 27 outputs the received frame to the transfer device 30a via the interface 28.

  Next, the functional configuration of the transfer device 30a will be described with reference to FIG. FIG. 11 is a diagram illustrating an example of a functional configuration of the transfer device. In the example illustrated in FIG. 11, the transfer device 30 a includes an interface information storage unit 31, a MAC learning table storage unit 32, and a roundabout packet identification information storage unit 33. In addition, the transfer device 30 a includes a plurality of interfaces 34 a to 34 c, a plurality of transmission / reception units 35 a to 35 c, a message identification unit 36, a roundabout communication determination unit 37, a route change notification unit 38, and a transfer processing unit 39.

  The interface information storage unit 31 stores interface information indicating whether or not the connection destination of each interface 34a to 34c is connected to a LAN other than the LAN 11a.

  FIG. 12 is a diagram illustrating an example of interface information. In the example shown in FIG. 12, the interface information storage unit 31 stores an interface identifier and inter-LAN communication information in association with each other. Here, the interface identifier is information for identifying each of the interfaces 34a to 34c. The inter-LAN communication information is information indicating whether each interface 34a to 34c is connected to a LAN other than the LAN 11a.

  For example, in the example illustrated in FIG. 12, the interface information storage unit 31 stores the interface identifier “IF # 1” indicating the interface 34a and the inter-LAN communication information “No” in association with each other. Further, the interface information storage unit 31 stores the interface identifier “IF # 2” indicating the interface 34b and the inter-LAN communication information “Yes” in association with each other. Further, the interface information storage unit 31 stores the interface identifier “IF # 3” indicating the interface 34c and the inter-LAN communication information “No” in association with each other.

  Returning to FIG. 11, the MAC learning table storage unit 32 stores a MAC learning table used by the transfer device 30a for frame transfer. For example, the MAC learning table storage unit 32 stores a MAC learning table illustrated in FIG.

  FIG. 13 is a diagram illustrating an example of the MAC learning table included in the transfer device. As illustrated in FIG. 13, the MAC learning table storage unit 32 stores a MAC learning table in which a MAC address is associated with an output interface. Here, the MAC address shown in FIG. 13 is the destination MAC address of the frame to be transferred, and the output interface is an interface identifier indicating the interface that sends out the frame to be transferred.

  For example, the MAC learning table storage unit 32 stores the MAC address “M1” of the server 40b and the interface identifier “IF # 2” of the interface 34b in association with each other. Further, the MAC learning table storage unit 32 stores the MAC address “M2” of the gateway 20a and the interface identifier “IF # 3” of the interface 34c in association with each other.

  Further, the MAC learning table storage unit 32 stores the MAC address “M3” of the server 40a and the interface identifier “IF # 1” of the interface 34a in association with each other. Further, the MAC learning table storage unit 32 stores the MAC address “M4” of the gateway 20b and the interface identifier “IF # 2” of the interface 34b in association with each other.

  Returning to FIG. 11, the roundabout packet identification information storage unit 33 determines a rule for determining whether or not a packet in a frame transmitted and received by the transfer device 30 a is a packet communication packet via a roundabout path, that is, a roundabout packet. Remember. For example, the roundabout packet identification information storage unit 33 stores the information packet identification information illustrated in FIG. 14 as a rule for determining whether or not the packet is a roundabout packet.

  FIG. 14 is a diagram illustrating an example of roundabout packet identification information stored in the transfer device. As illustrated in FIG. 14, the roundabout packet identification information storage unit 33 stores roundabout packet identification information in which target packets, detection rules, communication directions, and communication contents are associated. Here, the target packet indicates the type of packet used when determining whether or not the packet in the received frame is a roundabout packet.

  The detection rule indicates a condition for determining that the packet in the received frame is a roundabout packet. The communication direction indicates the communication direction of a frame used when determining whether or not the communication path is a roundabout path. The communication content is information for determining whether the transmission destination of the frame is a LAN other than the LAN 11a. Specifically, the communication information between the LANs of the interface that transmits the packet is “Yes”. It is information indicating whether or not.

  For example, in the example illustrated in FIG. 14, the roundabout packet identification information storage unit 33 includes the target packet “IP packet”, the detection rule “source IP address ≠ 192.168.0.0 / 24”, the communication direction “transmission”, The communication content “inter-LAN communication information = Yes” is stored in association with each other. As a result, when the roundabout packet identification information illustrated in FIG. 14 is stored, the transfer device 30a determines whether the connection destination of the interface that transmits the frame is a LAN other than the LAN 11a, that is, the LAN 11b, when transmitting the frame. To do.

  Further, when the connection destination of the interface that transmits the frame is the LAN 11b, the transfer device 30a determines the type of the packet in the frame to be transmitted. In addition, when the packet type is an IP packet, the transfer device 30a checks the source IP address of the packet. The transfer device 30a receives the IP address when the source IP address of the “IP packet” is not “192.168.0.0/24”, that is, when the external device of the subnet 10 is the source of the packet. It is determined that the packet in the received frame is a roundabout packet.

  The roundabout packet identification information stored in the roundabout packet identification information storage unit 33 is not limited to the information illustrated in FIG. That is, if it can be determined that the packet in the frame transmitted / received to / from the transfer device 30b of the LAN 11b is a packet related to communication between the servers 40a and 40b of the subnet 10 and the terminal device 2, an arbitrary condition is specified as the roundabout packet identification information. Can be set as

  For example, the transfer device 30a stores roundabout packet identification information in which the target packet is “IP packet”, the detection rule is “destination IP address ≠ 192.168.0.0 / 24”, and the communication direction is “reception”. Also good. That is, the transfer device 30a may determine that the received packet is a roundabout packet when the transmission destination of the IP packet received from the transfer device 30b is an external device of the subnet 10.

  Returning to FIG. 11, each of the interfaces 34 a to 34 c is a port included in the transfer device 30 a, for example, and performs packet transmission / reception with each connected device. Here, the interface 34a is connected to the server 40a. The interface 34b is connected to the transfer device 30b. The interface 34c is connected to the gateway 20a.

  Each transmission / reception part 35a-35c will output the received frame to the message identification part 36, if various frames are received from each interface 34a-34c. In addition, when the transmission / reception unit 35a receives a frame from the transfer processing unit 39, the transmission / reception unit 35a transmits the received frame to the server 40a. Further, when the transmission / reception unit 35b receives a frame from the transfer processing unit 39, the transmission / reception unit 35b transmits the received frame to the transfer device 30b. In addition, when the transmission / reception unit 35c receives a frame from the transfer processing unit 39, the transmission / reception unit 35c transmits the received frame to the gateway 20a.

  When the message identification unit 36 receives a frame from each of the transmission / reception units 35a to 35b, the message identification unit 36 determines the type of packet in the frame. Specifically, the message identification unit 36 determines whether the packet in the received frame is an IP packet, an ARP request, or an ARP response. Further, the message identification unit 36 confirms the target packet of the roundabout packet identification information stored in the roundabout packet identification information storage unit 33.

  If the packet type in the received frame matches the target packet of the roundabout packet identification information, the message identification unit 36 outputs the received frame to the roundabout communication determination unit 37 and the transfer processing unit 39. For example, when the type of packet in the received frame is “IP packet” and the target packet of the roundabout packet identification information is “IP packet”, the message identification unit 36 designates the received frame as the roundabout communication determination unit 37. To the transfer processing unit 39. On the other hand, the message identification unit 36 outputs the received frame to the transfer processing unit 39 when the type of the packet in the received frame does not match the target packet of the roundabout packet identification information.

  When the roundabout communication determination unit 37 receives a frame from the message identification unit 36, the roundabout communication determination unit 37 determines whether the packet is a roundabout packet according to the type of packet in the received frame, the source IP address, and the interface that transmits the packet. To do. Hereinafter, the function of the roundabout communication determination unit 37 will be specifically described.

  First, when receiving a frame from the message identification unit 36, the roundabout communication determination unit 37 acquires the roundabout packet identification information stored in the roundabout packet identification information storage unit 33. Then, the roundabout communication determination unit 37 determines whether the IP packet in the received frame is a packet that satisfies the detection rule of the roundabout packet identification information and the communication direction. Thereafter, when the IP packet in the received frame satisfies the roundabout packet identification information, the roundabout communication determination unit 37 outputs the IP packet in the frame to the path change notification unit 38. On the other hand, if the IP packet in the received frame does not satisfy the roundabout packet identification information, the roundabout communication determination unit 37 discards the received frame.

  Hereinafter, an example of processing executed by the roundabout communication determination unit 37 will be described. In the following description, an example in which the roundabout packet identification information storage unit 33 stores the roundabout packet identification information illustrated in FIG. 14 will be described. For example, the roundabout communication determination unit 37 determines whether or not the transmission source IP address of the IP packet in the frame is a value other than “192.168.0.0/24”. Further, when the transmission source IP address of the IP packet in the frame is a value other than “192.168.0.0/24”, the roundabout communication determination unit 37 identifies the destination MAC address of the received frame. Next, the roundabout communication determination unit 37 reads the interface identifier of the output interface associated with the identified destination MAC from the MAC learning table storage unit 32.

  Then, the roundabout communication determination unit 37 checks the interface information stored in the interface information storage unit 31, and determines whether or not the communication information between LANs associated with the read interface identifier is “Yes”. Thereafter, when the communication information between LANs associated with the read interface identifier is “Yes”, the roundabout communication determination unit 37 outputs the packet in the received frame to the route change notification unit 38.

  That is, when the transfer device 30a transmits a frame to the LAN 11b, the IP packet in the frame is related to communication between the terminal device 2 and each of the servers 40a and 40b based on the transmission source IP address of the IP packet in the frame. It is determined whether the packet is an IP packet. If the transfer device determines that the IP packet transmitted to the LAN 11 is an IP packet related to communication between the terminal device 2 and the subnet 10, the transfer device determines that the communication route is a roundabout route.

  When receiving the IP packet from the roundabout communication determining unit 37, the route change notifying unit 38 reads the source IP address and the destination IP address of the received IP packet. The route change notification unit 38 stores the read source IP address and destination IP address, and outputs a roundabout notification message with the roundabout flag set to “ON” to the transfer processing unit 39.

  The transfer processing unit 39 uses the MAC learning table stored in the MAC learning table storage unit 32 to execute the transfer process for the frame received from the message identification unit 36. Specifically, when receiving a frame from the message identification unit 36, the transfer processing unit 39 specifies an output interface associated with the destination MAC address of the received frame. Then, the transfer processing unit 39 outputs the received frame to the transmission / reception unit corresponding to the specified interface.

  Further, when receiving the roundabout notification message from the path change notification unit 38, the transfer processing unit 39 puts the received roundabout notification message in a frame and outputs it to the transmission / reception unit 35c. That is, the transfer processing unit 39 stores the roundabout notification message in a frame having the MAC address “M2” of the gateway 20a as the destination MAC address, and transmits the frame to the gateway 20a.

  Next, the flow of processing for determining whether or not the packet transmitted from the transfer device 30a to the transfer device 30b is a roundabout packet will be described with reference to FIG. FIG. 15 is a flowchart for explaining the flow of a roundabout packet determination process.

  First, when the transfer device 30a receives a frame from the gateway 20a, the transfer device 30b, or the server 40a (step S101), the transfer device 30a determines whether the type of the packet in the received frame is an IP packet (step S102). . When the type of the packet in the received frame is an IP packet (Yes in step S102), the transfer device 30a determines whether or not the transmission source IP address of the IP packet in the received frame satisfies the detection rule. Determination is made (step S103).

  In addition, when the transmission source IP address of the packet in the received frame satisfies the detection rule (Yes in step S103), the transfer device 30a determines whether to transmit the packet in the received frame to the transfer device 30b of the LAN 11b. Is determined (step S104). That is, the transfer device 30a determines whether or not to transmit a frame via a link connecting the LAN 11a and the LAN 11b. When the transfer device 30a transmits the received frame to the transfer device 30b of the LAN 11b (Yes at Step S104), the transfer device 30a determines that the packet in the received frame is a roundabout packet and sends a roundabout notification message to the terminal device 2. Transmit (step S105). Thereafter, the transfer device 30a ends the process.

  On the other hand, when the type of the packet in the received frame is not an IP packet (No in step S102), the transfer device 30a determines that the packet in the received frame is not a roundabout packet (step S106), and performs processing. finish. When the transmission source IP address of the packet in the received frame does not satisfy the detection rule (No at Step S103), the transfer device 30a determines that the packet in the received frame is not a roundabout packet (Step S106). ), The process is terminated. In addition, when transmitting the received frame to a device other than the transfer device 30b of the LAN 11b (No in Step S104), the transfer device 30a determines that the packet in the received frame is not a roundabout packet (Step S106). End the process.

[Effect of Example 1]
As described above, the transfer device 30a transmits and receives frames to and from the transfer device 30b included in the LAN 11b. Also, based on the transmission source IP address of the packet in the frame to be transmitted to the transfer device 30b, the transfer device 30a determines whether the packet in the frame to be transmitted is a packet related to packet communication between the server 40b and the terminal device 2. Determine whether or not. When the transfer device 30a determines that the packet in the frame to be transmitted is a packet related to packet communication between the server 40b and the terminal device 2, the transfer device 30a transmits a roundabout notification message to the terminal device 2.

  For this reason, the transfer device 30a can prevent packet communication via the roundabout path. Specifically, the transfer device 30a can determine whether or not the IP packet in the frame to be transmitted is a roundabout packet using only the network address of the subnet 10. As a result, the transfer device 30a can prevent packet communication via the bypass route without managing which of the LANs 11a and 11b the servers 40a and 40b are installed on.

  The network address of the subnet 10 is information that does not need to be changed once it is set. As a result, the communication system 1 can prevent packet communication via the roundabout path at a substantially constant management cost regardless of the number of servers and virtual machines included in the subnet 10.

  Further, the transfer device 30a performs packet communication between the terminal device 2 and the server 40b based on the transmission source IP address of the IP packet in the frame to be transmitted or the destination IP address of the IP packet in the received frame. It is determined whether the packet is related to. When the transfer device 30a determines that the packet in the frame transmitted and received with the transfer device 30b is a packet related to packet communication between the terminal device 2 and the server 40b, the transfer device 30a determines that the packet is a roundabout packet, A roundabout notification message is transmitted to the terminal device 2. As a result, the transfer device 30a can prevent packet communication via the roundabout path.

  When the transfer device 30a determines that the IP packet in the frame to be transmitted to the transfer device 30b is a roundabout packet, the transfer device 30a transmits a roundabout notification message to the terminal device 2 indicated by the source IP address of the IP packet. That is, when the same terminal device as the terminal device 2 accesses the subnet 10, the transfer device 30a can transmit the roundabout notification message only to the terminal device that performs packet communication on the roundabout path.

  In addition, the transfer device 30a instructs the terminal device 2 to switch the gateway when transmitting the IP packet to the server that is the destination of the IP packet determined to be a roundabout packet. For this reason, the transfer device 30a can shorten the communication path of each packet communication individually when the terminal device 2 performs packet communication with the plurality of servers 40a and 40b at the same time.

  Further, when the transmission source IP address of the IP packet in the frame to be transmitted is the IP address of the terminal device 2, the transfer device 30a transmits a roundabout notification message to the gateway 20a installed in the same LAN 11a as the transfer device 30a. . Then, when receiving the roundabout notification message, the gateway 20a transmits the received roundabout notification message to the terminal device 2 that is the transmission source of the IP packet determined to be the roundabout packet. For this reason, the gateway 20a can transmit a roundabout notification message so as to follow the same route as the IP packet transmitted by the terminal device 2.

  The transfer device 30a transmits a roundabout notification message via the gateway 20a. However, the embodiment is not limited to this. For example, the transfer device 30a acquires the IP address of the terminal device that is the transmission destination of the roundabout notification message from the IP packet in the frame transmitted and received with the transfer device 30b. In addition, the transfer device 30a acquires the MAC address of the terminal device that is the transmission destination of the roundabout notification message using the acquired IP address. Then, the transfer device 30a may store the roundabout notification message in a frame having the acquired MAC address as the destination MAC address, and directly transmit the frame to the terminal device.

  For example, when the transfer device 30a determines that the packet in the received frame is a roundabout packet, the transfer device 30a notifies the terminal device 2 of the gateway switching. However, the embodiment is not limited to this. For example, the transfer device 30a stores the IP address of the gateway 20b of the LAN 11b, and determines that the packet in the received frame is a roundabout packet, the gateway device 20b receives the IP address of the gateway 20b as the switching destination gateway. You may be notified.

  FIG. 16 is a diagram for explaining a first variation of the interface information. In the example illustrated in FIG. 16, the interface information storage unit 31 replaces the interface information illustrated in FIG. 12 with interface information in which an interface identifier, communication information between LANs, and an IP address of a gateway included in the connection destination LAN are associated. Remember.

  For example, the interface information storage unit 31 stores the interface identifier “IF # 2” of the interface 34b connected to the transfer device 30b of the LAN 11b and the inter-LAN communication information “Yes” in association with each other. Further, the interface information storage unit 31 stores the interface identifier “IF # 2” and the IP address “10.0.2.2” of the gateway 20b included in the LAN 11b in association with each other.

  When the roundabout communication determining unit 37 determines that the packet in the received frame is a roundabout packet, the roundabout communication determining unit 37 reads the IP address “10.0.2.2” of the gateway included in the connection destination LAN from the interface information. Then, the roundabout communication determination unit 37 notifies the route change notification unit 38 of the read gateway IP address “10.0.2.2”. Thereafter, the route change notification unit 38 generates a roundabout notification message in which the IP address “10.0.2.2” of the gateway 20b is stored.

  Here, FIG. 17 is a diagram illustrating variations in the format of the roundabout notification message. As illustrated in FIG. 17, the roundabout communication determination unit 37 generates a roundabout notification message in which the IP address “10.0.2.2” of the gateway is stored in the roundabout notification message illustrated in FIG. Output to. Then, the transfer processing unit 39 stores the roundabout notification message in which the IP address of the gateway 20 b is stored in the frame, and transmits the frame to the terminal device 2.

  As a result, the routing table update unit 19 of the terminal device 2 updates the routing table 12a as shown in FIG. FIG. 18 is a diagram for explaining a variation of the updated routing table. In the example illustrated in FIG. 18, the routing table update unit 19 receives a frame in which a roundabout notification message illustrated in FIG. 17 is stored. In such a case, the routing table update unit 19 extracts the roundabout notification message from the received frame, and stores the destination IP address of the extracted roundabout notification message and the mask value “192.168.0.2/32”. Add

  The routing table update unit 19 stores the gateway IP address “10.0.2.2” stored in the roundabout notification message in the added entry. In addition, the routing table update unit 19 transmits a packet having a destination IP address “192.168.0.2” so that the gateway 20b is selected so that the communication cost is lower than other communication costs. Store “5” in the added entry.

  Further, the transfer device 30a may determine whether or not the packet in the received frame is a roundabout packet depending on whether or not a failure has occurred in the gateway 20b. Hereinafter, processing for determining whether or not a packet in a received frame is a roundabout packet depending on whether or not a failure has occurred in the gateway 20b will be described.

  FIG. 19 is a diagram for explaining a second variation of the interface information. As illustrated in FIG. 19, the transfer device 30 a stores a failure flag in association with each entry of the interface information illustrated in FIG. 16. Here, the failure flag is a flag indicating whether or not a failure has occurred in the gateway to which the associated IP address is assigned. For example, in the example shown in FIG. 19, the inter-LAN communication information “Yes”, the IP address “10.0.2.2” of the gateway 20b, and the failure flag “ON” are stored in the interface identifier “IF # 2”. . For this reason, the transfer device 30a can determine that a failure has occurred in the gateway 20b.

  In addition, the transfer device 30a may determine whether or not a failure has occurred in the gateway 20a. If a failure has occurred, the transfer device 30a may notify the transfer device 30b that a failure has occurred in the gateway 20a. For example, the transfer device 30a transmits a ping message to the gateway 20a at predetermined time intervals. When the number of times that the response to the ping message cannot be received from the gateway 20a exceeds a predetermined number, the transfer device 30a determines that a failure has occurred in the gateway 20a.

  Thereafter, when a failure occurs in the gateway 20a, the transfer device 30a notifies the transfer device 30b that a failure has occurred in the gateway 20a and the IP address “10.10.1.1.1” of the gateway 20a. To do. Similarly, the transfer device 30b determines whether or not a failure has occurred in the gateway 20b. If a failure has occurred, the transfer device 30b notifies the transfer device 30a that a failure has occurred in the gateway 20b.

  For example, if the transfer device 30b determines that a failure has occurred in the gateway 20b, the transfer device 30a notifies the transfer device 30a that a failure has occurred in the gateway 20b and the IP address “10.0.2.2” of the gateway 20b. To the transfer device 30a. When the transfer device 30a receives a notification that a failure has occurred in the gateway 20b from the transfer device 30b, the entry in which the IP address “10.0.2.2” of the gateway 20b is stored from the interface information. Search for. Thereafter, the transfer device 30a changes the failure flag of the searched entry to “ON”.

  Further, when receiving the frame in which the IP packet is stored, the transfer device 30a determines whether or not an interface that transmits the IP packet in the frame is connected to the transfer device 30b of the LAN 11b. In addition, when the interface that transmits the IP packet in the frame is connected to the transfer device 30b of the LAN 11b, the transfer device 30a determines whether the IP packet source IP address is within the network address range of the subnet 10. Determine whether or not.

  Further, when the source IP address of the IP packet in the frame is not the IP address of the subnet 10, the transfer device 30a determines whether or not the failure flag associated with the interface identifier of the interface that transmits the frame is “ON”. Determine. When the failure flag associated with the interface identifier of the interface that transmits the IP packet in the frame is “ON”, the transfer device 30a relays the frame. On the other hand, the transfer device 30a relays the frame and transmits a roundabout notification message to the terminal device 2 when the failure flag is “OFF”.

  That is, when the transfer device 30a transmits an IP packet related to packet communication between the terminal device 2 and the server 40b to the transfer device 30b, if the gateway 20b has a failure, the communication route is not a roundabout route. Is determined. For this reason, when a failure occurs in the gateway 20b, the transfer device 30a does not prevent packet communication between the LAN 11b and the terminal device 2 via the roundabout path. As a result, the transfer device 30a can continue packet communication between the subnet 10 and the terminal device 2 even when one of the gateways 20a and 20b fails.

  Note that the processing described above may be realized by adding a new functional configuration to the transfer device 30a. For example, the transfer processing unit 39, the message identification unit 36, and the roundabout communication determination unit 37 are emphasized and realized. May be. For example, the transfer processing unit 39 transmits a ping to the gateway 20a.

  Further, the message identification unit 36 outputs a response from the gateway 20 a to the roundabout communication determination unit 37. When there is no response from the gateway 20a a predetermined number of times, the roundabout communication determination unit 37 notifies the transfer device 30b that the gateway 20a has failed via the route change notification unit 38 and the transfer processing unit 39. You may be notified.

  Further, the message identification unit 36 outputs a notification that the gateway 20b has failed to the roundabout communication determination unit 37. When the roundabout communication determination unit 37 receives the notification that the gateway 20b has failed, the roundabout communication determination unit 37 sets the failure flag associated with the IP address of the gateway 20b to “ON”.

  Next, the flow of processing for determining whether a packet is a roundabout packet according to whether or not each gateway 20a, 20b has failed will be described using FIG. FIG. 20 is a flowchart for explaining a variation of the roundabout packet determination process. In the example illustrated in FIG. 20, the transfer device 30a stores the roundabout packet identification information illustrated in FIG.

  First, when the transfer device 30a receives a frame from the gateway 20a, the transfer device 30b, or the server 40a (step S201), the transfer device 30a determines whether the type of the packet in the received frame is an IP packet (step S202). . When the type of the packet in the received frame is an IP packet (Yes at Step S202), the transfer device 30a determines whether or not the transmission source IP address of the IP packet in the received frame satisfies the detection rule. Determination is made (step S203).

  In addition, when the transmission source IP address of the IP packet in the frame satisfies the detection rule (Yes in step S203), the transfer device 30a determines whether to transmit the IP packet in the frame to the transfer device 30b ( Step S204). When transmitting the IP packet in the received frame to the transfer device 30b (Yes at Step S204), the transfer device 30a determines whether or not a failure has occurred in the gateway 20b of the LAN 11b (Step S205). Thereafter, when no failure has occurred in the gateway 20b of the LAN 11b (No at Step S205), the transfer device 30a executes the following processing. That is, the transfer device 30a determines that the IP packet in the received frame is a roundabout packet, transmits a roundabout notification message to the terminal device 2 (step S206), and ends the process.

  On the other hand, when the type of the IP packet in the received frame is not an IP packet (No at Step S202), the transfer device 30a determines that the IP packet in the received frame is not a roundabout packet (Step S207). End the process. If the source IP address of the IP packet in the received frame does not satisfy the detection rule (No at Step S203), the transfer device 30a determines that the IP packet in the received frame is not a roundabout packet ( Step S207) and the process is terminated.

  When the transfer device 30a does not transmit the received IP packet to the LAN 11b (No at Step S204), the transfer device 30a determines that the IP packet in the received frame is not a roundabout packet (Step S207), and ends the process. In addition, when a failure occurs in the gateway 20b of the LAN 11b (Yes at Step S205), the transfer device 30a determines that the IP packet in the received frame is not a roundabout packet (Step S207) and ends the processing. To do.

  In the above description, the example in which the transfer device 30a transmits the roundabout notification message to the terminal device 2 has been described. However, the embodiment is not limited thereto. For example, FIG. 21 is a diagram illustrating a variation of the communication system. As illustrated in FIG. 21, the network 3 of the communication system 1 includes a router 3 a that relays packet communication between the terminal device 2 and the subnet 10.

  For example, the router 3 a stores the routing table shown in FIG. 4A instead of the terminal device 2. In addition, when the router 3a receives a frame storing an IP packet having the IP address of the subnet 10 as the destination IP address from the terminal device 2, the router 3a receives the frame of the gateway associated with the destination IP address of the IP packet in the received frame. Identify the IP address. Then, the router 3a acquires the MAC address of the gateway using the identified IP address, and relays the frame using the acquired MAC address.

  Here, when the router 3 a is installed in the network 3, the transfer device 30 a transmits a roundabout notification message to the router 3 a instead of the terminal device 2. As a result, since the router 3a updates the routing table in the same manner as the routing table update unit 19, it is possible to switch the gateway for packet communication via the roundabout path.

[Effect of Example 2]
As described above, the transfer device 30a stores the IP address of the gateway 20b of the LAN 11b having the transfer device 30b as the interface information of the interface connected to the transfer device 30b. If the transfer device 30a determines that the IP packet to be transmitted to the transfer device 30b is a roundabout packet, the transfer device 30a transmits a roundabout notification message storing the IP address of the gateway 20b to the terminal device 2.

  For this reason, the transfer device 30a can notify the gateway to which the terminal device 2 should transmit the IP packet. As a result, the transfer device 30a can prevent packet communication via the delay path even when the subnet 10 has three or more LANs.

  The transfer device 30a can adopt arbitrary roundabout packet identification information, but depending on the roundabout packet identification information adopted, the gateway that relays the roundabout packet is a gateway 20a included in the same LAN as the transfer device 30a. You can decide whether or not there is. For example, when the transmission source IP address of the IP packet in the frame transmitted to the transfer device 30b is the IP address of the terminal device 2, the transfer device 30a transfers the IP packet in the frame via the gateway 20a. It can be determined that the packet is a roundabout packet. Further, when the transmission source IP address of the IP packet in the frame received from the transfer device 30b is the IP address of the terminal device 2, the transfer device 30a bypasses the IP packet in the frame transferred via the gateway 20b. It can be determined that it is a packet.

  Here, the transfer device 30a stores the IP address of the gateway 20b, but does not store the IP address of the gateway 20a. Therefore, the transfer device 30a stores roundabout packet identification information that can determine whether or not a packet transferred through the gateway 20a is a roundabout packet. When the transfer device 30a determines that the packet to be transferred is a roundabout packet, the transfer device 30a determines that the transfer route via the gateway 20a is a roundabout route, and notifies the terminal device 2 of the IP address of the gateway 20b. As a result, the transfer device 30a can eliminate the roundabout path via the gateway 20a installed in the same LAN 11a.

  Further, the transfer device 30b determines whether or not a failure has occurred in the gateway 20b installed in the same LAN 11b. If it is determined that a failure has occurred in the gateway 20b, the transfer device 30b has the gateway 20b in the transfer device 30a. Notify that there is a failure. In such a case, the transfer device 30a stores information that the gateway 20b has failed.

  If the transfer device 30a determines that the IP packet in the frame transferred to the transfer device 30b is an IP packet related to packet communication between the terminal device 2 and the server 40b, it determines whether or not the transfer device 30b is out of order. Determine. When the transfer device 30a determines that the transfer device 30b has not failed, the transfer device 30a transmits a roundabout notification message to the terminal device 2, and when the transfer device 30b determines that the transfer device 30b has failed, Do not send roundabout notification messages.

  As described above, when the gateway 20b breaks down, the transfer device 30a determines that the packet communication path is not a roundabout path even if the packet communication IP packet to be passed through the gateway 20b passes through the gateway 20a. . For this reason, as a result of preventing the gateway device in which the terminal device 2 has failed from being selected as a priority gateway, the transfer device 30a can continue packet communication between the terminal device 2 and the subnet 10 even when the gateway fails. .

  When there is a router 3a that relays packet communication between the terminal device 2 and each of the gateways 20a and 20b, the transfer device 30a transmits a roundabout notification message to the router 3a. For this reason, the transfer device 30a can prevent the communication route from being a roundabout route even when the router 3a routes a packet related to packet communication between the terminal device 2 and each of the gateways 20a and 20b.

  In the third embodiment, a transfer device that determines whether or not a packet communication route is a roundabout route using a destination address of an ARP response in a frame received from another LAN will be described.

  FIG. 22 is a schematic diagram illustrating a communication system according to a third embodiment. In addition, the terminal device 2, the network 3, and each server 40a, 40b of the communication system 1a shown in FIG. 22 shall exhibit the function similar to the terminal device 2, the network 3, and each server 40a, 40b shown in FIG. Description is omitted. In the example illustrated in FIG. 22, the LAN 11a includes a transfer device 30c. Further, the LAN 11b has a transfer device 30d. Note that the transfer device 30d performs the same function as the transfer device 30c, and the following description is omitted.

  Similar to the gateway 20a, the gateway 20c relays IP packets related to packet communication between the servers 40a and 40b and the terminal device 2. Further, when transmitting the ARP request, the gateway 20c stores the destination IP address and the source IP address of the IP packet that triggered the ARP request in association with each other.

  When receiving the roundabout notification message from the transfer device 30c, the gateway 20c identifies the transmission source IP address stored in association with the destination IP address included in the received roundabout notification message. Thereafter, the gateway 20c transmits a roundabout notification message with the identified source IP address as a destination.

  The transfer device 30c determines whether the communication path is a roundabout path depending on whether the packet in the frame transmitted / received to / from the transfer device 30d of the LAN 11b is a packet related to packet communication between the servers 40a and 40b and the terminal device 2. Determine whether. Specifically, the transfer device 30c determines whether the communication path is a roundabout path according to whether the transmission destination of the ARP response in the frame received from the transfer device 30d is the gateway 20c.

  Hereinafter, the function of the transfer device 30c will be described in detail. In the following description, it is assumed that the terminal device 2 has transmitted a frame storing an IP packet destined for the server 40b to the gateway 20c. For example, the gateway 20c receives a frame in which an IP packet having a transmission source IP address “10.0.0.1” and a destination IP address “192.168.0.2” is stored. In such a case, the gateway 20c stores the destination IP address and the source IP address of the IP packet in the received frame in association with each other. Then, the gateway 20 c broadcasts the frame in which the ARP request storing the received destination IP address “192.168.0.2” is stored in the subnet 10.

  As a result, the transfer device 30c transfers the frame in which the ARP request is stored to the transfer device 30d. The transfer device 30d transfers the frame in which the ARP request is stored to the server 40b. In such a case, since the destination IP address of the ARP request in the received frame matches the IP address “192.168.0.2” of the server 40b, the server 40b changes the MAC address “M1” of the server 40b. A stored ARP response is generated.

  Then, the server 40b stores the ARP response in the frame having the source MAC address, that is, the MAC address of the gateway 20c as the destination MAC address in the ARP request, and transmits the frame to the transfer device 30d. As a result, the gateway 20c receives the frame in which the ARP response is stored via the transfer device 30d and the transfer device 30c. In the following description, receiving a frame in which an ARP response is stored may be described as receiving an ARP response.

  Here, when receiving the frame in which the ARP response is stored from the transfer device 30d, the transfer device 30c determines whether the destination MAC address of the ARP response in the received frame matches the MAC address of the gateway 20c. . When the destination MAC address of the ARP response in the frame matches the MAC address of the gateway 20c, the transfer device 30c reads the transmission source IP address from the ARP request in the frame. Thereafter, the transfer device 30c stores a roundabout notification message in which the read source IP address is stored in the destination IP address in a frame addressed to the gateway 20c, and transmits the frame to the gateway 20c.

  When receiving the frame in which the roundabout notification message is stored from the transfer device 30c, the gateway 20c reads the transmission source IP address stored in the roundabout notification message in the received frame. Then, the gateway 20c identifies a destination IP address to be stored in association with the read source IP address. Thereafter, the gateway 20c stores the identified destination IP address in the roundabout notification message, and transmits the roundabout notification message to the terminal device 2.

  That is, when the transfer device 30c receives a frame in which an ARP response addressed to the gateway 20c is stored from the transfer device 30d, the transfer device 30c determines that the gateway 20c has received an IP packet addressed to the server 40b from the terminal device 2. it can. Here, when the gateway 20c receives an IP packet destined for the server 40b from the terminal device 2, the frame storing the IP packet destined for the server 40b from the terminal device 2 is transferred from the LAN 11a to the LAN 11b. The communication path becomes a roundabout path. For this reason, when the transfer device 30c receives from the transfer device 30d the frame in which the ARP response addressed to the gateway 20c is stored, the communication path related to the IP packet that triggered the transmission of the ARP response is a roundabout route. judge.

  Hereinafter, an example of functional configurations of the gateway 20c and the transfer device 30c according to the third embodiment will be described with reference to the drawings. First, an example of a functional configuration of the gateway 20c will be described with reference to FIG.

  FIG. 23 is a schematic diagram illustrating an example of a functional configuration of a gateway according to the third embodiment. As shown in FIG. 23, the gateway 20c includes a plurality of interfaces 21, 28, a plurality of transmission / reception units 22, 27, a message identification unit 23, a roundabout communication identification unit 24a, a route change notification unit 25a, a transfer processing unit 26a, and address correspondence. It has a table storage unit 29b. Each interface 21, 28, each transmission / reception unit 22, 27, and message identification unit 23 exhibits the same function as each interface 21, 28, each transmission / reception unit 22, 27, message identification unit 23 shown in FIG. The description is omitted.

  The address correspondence table storage unit 29b stores the source IP address and the destination IP address of the IP packet in the frame received by the gateway 20c in association with each other. For example, FIG. 24 is a schematic diagram illustrating an example of an address correspondence table stored in the gateway according to the third embodiment. For example, as shown in FIG. 24, the address correspondence table storage unit 29b stores the source IP address “10.0.0.1” and the destination IP address “192.168.0.2” in association with each other. .

  Returning to FIG. 23, when receiving the IP packet from the message identification unit 23, the transfer processing unit 26 a executes the packet transfer process of the gateway 20 c as with the transfer processing unit 26. For example, when receiving the IP packet from the message identification unit 23, the transfer processing unit 26a associates the source IP address and the destination IP address of the IP packet in the received frame and stores them in the address correspondence table storage unit 29b.

  Then, the transfer processing unit 26a uses the MAC address of the gateway 20c as a transmission source MAC address, and generates an ARP request that stores the destination IP address of the IP packet. Further, the transfer processing unit 26 a stores the ARP request in a frame and outputs the frame to the transmission / reception unit 27. Further, when receiving the frame in which the ARP response is stored, the transfer processing unit 26a generates a frame with the transmission source MAC address of the ARP response in the frame as the destination MAC address. Then, the transfer processing unit 26 a stores the IP packet received from the message identification unit 23 in the generated frame, and outputs the frame storing the IP packet to the transmission / reception unit 27.

  When the roundabout communication specifying unit 24a receives the roundabout notification message from the message identifying unit 23, the roundabout communication specifying unit 24a acquires the transmission source protocol address from the received roundabout notification message. Further, the roundabout communication specifying unit 24a reads the source IP address stored in association with the acquired source protocol address from the address correspondence table storage unit 29b.

  In other words, the roundabout communication specifying unit 24a uses the source protocol address of the ARP response in the received frame to read the source IP address of the IP packet that triggered the issuance of the ARP request from the address correspondence table storage unit 29b. . Then, the roundabout communication specifying unit 24a outputs the read source IP address and the roundabout notification message to the route change notification unit 25a.

  When the route change notification unit 25a receives the roundabout notification message and the transmission source IP address from the roundabout communication identification unit 24a, the route change notification unit 25a uses the received transmission source IP address to transmit the roundabout notification message. Get the MAC address. Then, the route change notification unit 25a generates a frame having the acquired MAC address as the destination MAC address, and stores a roundabout notification message in the generated frame. Thereafter, the route change notification unit 25 a outputs a frame storing the roundabout notification message to the transmission / reception unit 22.

  FIG. 25 is a schematic diagram illustrating an example of a format of a roundabout notification message according to the third embodiment. As shown in FIG. 25, the route change notification unit 25a generates a roundabout notification message storing the destination IP address of the IP packet and the roundabout flag. When the route change notification unit 25a receives the IP address “10.0.0.1” of the terminal device 2 from the roundabout communication specifying unit 24a, the route change notification unit 25a uses the received IP address “10.0.0.1”. The MAC address of the terminal device 2 is acquired.

  Then, the route change notification unit 25 a stores the roundabout notification message in a frame with the acquired MAC address as the destination MAC address, and outputs the frame to the network 3. As a result, in the example illustrated in FIG. 25, the route change notification unit 25 a indicates to the terminal device 2 that the communication route of the IP packet having the IP address “192.168.0.2” as the destination IP address is a roundabout route. Can be notified.

  Next, the functional configuration of the transfer device 30c will be described with reference to FIG. FIG. 26 is a schematic diagram illustrating an example of a functional configuration of the transfer apparatus according to the third embodiment. In the example illustrated in FIG. 26, the transfer device 30c includes an interface information storage unit 31, a MAC learning table storage unit 32, and a roundabout packet identification information storage unit 33a. In addition, the transfer device 30 c includes a plurality of interfaces 34 a to 34 c, a plurality of transmission / reception units 35 a to 35 c, a message identification unit 36, a roundabout communication determination unit 37 a, a route change notification unit 38, and a transfer processing unit 39.

  Note that the interface information storage unit 31 and the MAC learning table storage unit 32 store the same information as in the first embodiment, and a description thereof will be omitted. Further, the interfaces 34a to 34c, the transmission / reception units 35a to 35c, the message identification unit 36, the route change notification unit 38, and the transfer processing unit 39 are omitted because they exhibit the same functions as those in the first embodiment.

  For example, the transfer device 30c includes a roundabout packet identification information storage unit 33a and a roundabout communication determination unit 37a. Similar to the roundabout packet identification information storage unit 33, the roundabout packet identification information storage unit 33a stores a rule for determining whether or not a packet in a frame transferred by the transfer device 30c is a roundabout packet.

  FIG. 27 is a schematic diagram illustrating an example of roundabout packet identification information stored in the transfer apparatus according to the third embodiment. In the example shown in FIG. 27, the roundabout packet identification information storage unit 33a has “ARP response” as the target packet, “destination MAC address = M2” as the detection rule, “reception” as the communication direction, and “inter-LAN communication information” as the communication content. = Yes "is stored. As a result, when the ARP response is stored in the frame received from the LAN other than the LAN 11a and the destination MAC address of the ARP response in the frame is “M2”, the transfer device 30c has the ARP in the received frame. It is determined that the response is a roundabout packet.

  When the roundabout communication determination unit 37a receives a frame from the message identification unit 36, the roundabout communication determination unit 37a determines whether the type of the packet in the frame is an ARP response. The roundabout communication determination unit 37a determines whether or not the ARP response is stored in the received frame, and the ARP response in the frame satisfies the detection rule of the roundabout packet identification information, the communication direction, and the communication content. . Thereafter, when the ARP response in the received frame satisfies the roundabout packet identification information, the roundabout communication determination unit 37a outputs the ARP response in the received frame to the path change notification unit 38. On the other hand, when the ARP response in the received frame does not satisfy the roundabout packet identification information, the roundabout communication determination unit 37a discards the received ARP response.

  Hereinafter, an example of processing performed by the roundabout communication determination unit 37a will be described. In the following description, an example in which the roundabout packet identification information storage unit 33a stores the roundabout packet identification information illustrated in FIG. 27 will be described. For example, since the detection rule of the roundabout packet identification information is “destination MAC address = M2”, the roundabout communication determination unit 37a determines whether the destination MAC address of the ARP response in the frame is “M2”.

  Further, when the destination MAC address of the ARP response in the frame is “M2”, the roundabout communication determination unit 37a receives the frame from the source MAC address because the communication direction of the roundabout packet identification information is “reception”. Identifies the received interface. For example, the roundabout communication determination unit 37a reads the interface identifier associated with the frame transmission source MAC address from the MAC learning table storage unit 32.

  Then, the roundabout communication determination unit 37a checks the interface information storage unit 31 and determines whether or not the communication information between LANs associated with the interface identifier read from the MAC learning table storage unit 32 is “Yes”. . That is, the roundabout communication determination unit 37a determines whether the interface that has received the frame in which the ARP response is stored is an interface connected to a LAN other than the LAN 11a. Thereafter, when the communication information between LANs associated with the read interface identifier is “Yes”, the roundabout communication determination unit 37a outputs an ARP response in the frame to the path change notification unit 38.

  That is, when receiving the frame in which the ARP response is stored from the LAN 11b, the transfer device 30c determines whether or not the destination MAC address is the MAC address of the gateway 20c. Here, when the destination MAC address of the ARP response in the frame is the MAC address of the gateway 20c, the gateway 20c is considered to have received from the terminal device 2 an IP packet destined for the server 40b of the LAN 11b.

  Therefore, when the transfer device 30c receives a frame in which the ARP response is stored from the LAN 11b, and the destination MAC address is the MAC address of the gateway 20c, the transfer device 30c determines that the ARP response in the received frame is a roundabout packet. judge. Then, the transfer device 30c transmits a roundabout notification message to the gateway 20c.

  As a result, the gateway 20c transmits a roundabout notification message to the terminal device 2 using the source IP address of the IP packet that triggered the ARP response. As a result, the transfer device 30c can transmit a roundabout notification message to the terminal device 2 even when the communication route is determined to be a roundabout route using the ARP response.

  Next, the flow of processing for determining whether the communication path is a roundabout path using the ARP response in the frame received by the transfer apparatus 30c from the transfer apparatus 30d will be described with reference to FIG. FIG. 28 is a flowchart for explaining the flow of the roundabout packet determination process according to the third embodiment.

  First, when the transfer device 30c receives a frame from the gateway 20c, the transfer device 30d, or the server 40a (step S301), the transfer device 30c determines whether the type of the packet in the received frame is an ARP response (step S302). . When the type of the packet in the received frame is an ARP response (Yes in step S302), the transfer device 30c determines whether the destination MAC address of the ARP response in the received frame satisfies the detection rule. (Step S303).

  In addition, when the destination MAC address of the ARP response in the received frame satisfies the detection rule (Yes at Step S303), the transfer device 30c determines whether or not the frame is received from the transfer device 30d of the LAN 11b (Step S303). S304). That is, the transfer device 30c determines whether or not a frame in which an ARP response is stored is received via a link connecting the LAN 11a and the LAN 11b. When the transfer device 30c receives the frame in which the ARP response is stored from the transfer device 30b of the LAN 11b (Yes in step S304), the transfer device 30c determines that the communication route is a roundabout route and sends a roundabout notification message to the terminal device 2. Transmit (step S305), and the process ends.

  On the other hand, when the type of the packet in the received frame is not an ARP response (No at Step S302), the transfer device 30c determines that the packet is not a roundabout packet (Step S306) and ends the process. If the destination MAC address of the ARP response in the received frame does not satisfy the detection rule (No at Step S303), the transfer device 30c determines that the packet is not a roundabout packet (Step S306), and ends the process. If the transfer device 30c receives a frame in which an ARP response is stored from a device other than the LAN 11b transfer device 30d (No in step S304), the transfer device 30c determines that the packet is not a roundabout packet (step S306) and ends the process. To do.

[Effect of Example 3]
Thus, the transfer device 30c can determine whether or not the communication path is a roundabout path based on the ARP response in the frame received from the transfer apparatus 30d. For example, when the destination MAC address of the ARP response in the frame received from the transfer device 30d or the destination MAC address of the ARP response transmitted to the transfer device 30d is a gateway, the transfer device 30c receives the ARP response in the frame. It is determined that the packet is a roundabout packet.

  For this reason, since the transfer device 30c can switch the gateway to which the terminal device 2 transmits the packet before the IP packet flows through the roundabout path, the traffic in the subnet 10 can be reduced.

  In addition, the transfer device 30c transmits a roundabout notification message storing the destination IP address of the IP packet via the roundabout route to the terminal device 2 via the gateway 20c. That is, the transfer device 30c instructs the gateway 20c to which the destination MAC address of the ARP response in the received frame is assigned to transmit a roundabout notification message.

  Then, the gateway 20c generates a roundabout notification message packet and transmits the packet to the terminal device 2 that is the source of the packet communication related to the ARP response. For this reason, when the terminal device 2 performs packet communication with the plurality of servers 40a and 40b included in the subnet 10, the transfer device 30c can notify which packet communication is via the roundabout path.

  Specifically, the gateway 20c stores the destination IP address and the source IP address of the IP packet in association with each other. Then, the gateway 20c uses the source IP address stored in association with the same destination IP address as the source protocol address stored in the roundabout notification message to determine the MAC address of the terminal device that is the source of the IP packet. get. Thereafter, the gateway 20c stores the roundabout notification message in a frame having the acquired MAC address as the destination MAC address and transmits the message. Therefore, the gateway 20c can transmit a roundabout notification message to the transmission source of the IP packet even when the transfer device 30c detects the roundabout packet using the ARP response.

  In addition, when receiving the roundabout notification message from the gateway 20c, the terminal device 2 switches the gateway used when transmitting the IP packet to the server indicated by the IP address stored in the roundabout notification message. As a result, even when a plurality of terminal devices similar to the terminal device 2 access the subnet 10, the transfer device 30c transmits a roundabout notification message only to the terminal device that performs packet communication via the roundabout path. be able to.

  In the fourth embodiment, a variation of the communication system 1a according to the third embodiment will be described. For example, the gateway 20c transmits a roundabout communication message shown in FIG. However, the embodiment is not limited to this, and a roundabout notification message including the IP address of the switching destination gateway may be transmitted in the same manner as the variation of the transfer device 30a described in the second embodiment.

  For example, the transfer device 30c stores, as interface information, an IP address assigned to a LAN gateway including a connection destination device in association with an interface identifier and inter-LAN communication information. If the transfer device 30c determines that the ARP request in the received frame is a roundabout packet, the transfer device 30c acquires the IP address of the gateway associated with the interface identifier of the interface that has received the frame. Thereafter, the transfer device 30c may generate a roundabout notification message including the acquired IP address and transmit a frame storing the generated roundabout notification message to the gateway 20c. As a result, the transfer device 30c can notify the terminal device 2 of the IP address of the switching destination gateway.

  The gateway 20a may include a roundabout flag in the ARP cache table. For example, the gateway 20a stores an ARP cache table in which the source MAC address acquired from the ARP response is used as the destination MAC address and the source protocol address is used as the destination IP address. Further, the gateway 20a stores a roundabout flag indicating whether or not the IP packet storing the associated destination IP address is a roundabout packet in the ARP cache table. Then, the gateway 20a uses the roundabout flag stored in the ARP cache table to determine whether or not the packet in the received frame is a roundabout packet.

  Hereinafter, the gateway 20c that determines whether the packet in the received frame is a roundabout packet using the ARP cache table will be described. First, variations in the functional configuration of the gateway 20c will be described with reference to FIG. FIG. 29 is a diagram for explaining a variation of the functional configuration of the gateway. As illustrated in FIG. 29, the gateway 20c includes an ARP cache table storage unit 29a.

  Here, FIG. 30 is a diagram for explaining a variation of the ARP cache table stored in the gateway. As illustrated in FIG. 30, the ARP cache table storage unit 29a stores an ARP cache table in which a destination IP address, a MAC address, and a roundabout flag are associated with each other. In the example illustrated in FIG. 30, the ARP cache table storage unit 29a stores an ARP cache table in which a destination IP address “192.168.0.2”, a MAC address “M1”, and a roundabout flag “OFF” are associated with each other.

  The transfer processing unit 26a performs IP packet transfer processing using the ARP cache table storage unit 29a described above. That is, the transfer processing unit 26a determines whether or not the destination IP address of the IP packet in the frame received from the message identifying unit 23 is stored in the ARP cache table.

  If the destination IP address of the IP packet in the received frame is not stored in the ARP cache table storage unit 29a, the transfer processing unit 26a issues a frame in which the ARP request is stored. Then, when receiving the frame in which the ARP response is stored, the transfer processing unit 26a associates the transmission source protocol address, the transmission source MAC address, and the roundabout flag “OFF” of the received ARP response with each other, and the ARP cache table storage unit 29a.

  Here, in addition to the processing described above, the roundabout communication specifying unit 24a changes the roundabout flag stored in association with the destination IP address of the roundabout notification message to “ON” when receiving the roundabout notification message. When the destination IP address of the IP packet in the newly received frame is stored in the ARP cache table storage unit 29a, the transfer processing unit 26a sets the roundabout flag associated with the destination IP address to “ON”. It is determined whether or not.

  Here, when the roundabout flag associated with the destination IP address is “ON”, the transfer processing unit 26a transmits a roundabout notification message to the transmission source of the newly received frame. Specifically, the transfer processing unit 26a generates a frame with the transmission source MAC address of the received frame as the destination MAC address. Further, the transfer processing unit 26a generates a roundabout notification message storing the destination IP address of the IP packet in the received frame and the roundabout flag “ON”. Then, the transfer processing unit 26 a stores the generated roundabout notification message in the generated frame and outputs it to the network 3.

[Effect of Example 4]
As described above, the gateway 20c includes the ARP cache table storage unit 29a that stores a pair of the transmission source protocol address and the transmission source MAC address stored in the ARP response in association with the roundabout flag. When receiving the roundabout notification message from the transfer device 30c, the gateway 20c sets the roundabout flag associated with the destination IP address of the roundabout notification message to “ON”.

  Thereafter, when the ARP cache table storage unit 29a stores the destination IP address of the IP packet in the frame and the detour flag “ON” in association with each other, the gateway 20c notifies the detour to the frame transmission source. Send a message.

  For this reason, every time the gateway 20c receives a plurality of IP packets destined for the server 40b from an external device in the subnet 10, it determines whether or not the IP packet is a roundabout packet without issuing an ARP request. be able to. Further, the gateway 20c can promptly transmit a roundabout notification message to the external device when receiving a frame in which the roundabout packet is stored.

  In the fifth embodiment, a communication system 1b in which a transfer apparatus connects a LAN having a gateway and a LAN not having a gateway will be described.

  FIG. 31 is a schematic diagram illustrating a communication system according to a fifth embodiment. In the example illustrated in FIG. 31, the communication system 1 b includes a terminal device 2, a network 3, a first base 4, a second base 5, and a third base 6. The first base 4 has a LAN 11a. The second base 5 has a LAN 11b. The third base 6 has a LAN 11c.

  The LAN 11a includes a LAN 11a having a gateway 20a, a transfer device 30e, and a server 40a. The LAN 11b includes a gateway 20b, a transfer device 30f, and a server 40b. The LAN 11c does not have a gateway, but includes a transfer device 30g and a server 40c. Here, the IP address “192.168.0.3” is assigned to the server 40c.

  The transfer device 30e is connected to the gateway 20a, the server 40a, the transfer device 30f, and the transfer device 30g. The transfer device 30f is connected to the gateway 20b, the transfer device 30e, and the server 40b. The transfer device 30g is connected to the transfer device 30e and the server 40c. Therefore, the terminal device 2 performs packet communication with the server 40c via the gateway 20a, the transfer device 30e, and the transfer device 30g.

  Hereinafter, functions of the transfer device 30e included in the communication system 1b will be described. The terminal device 2, the network 3, and the servers 40a and 40b shown in FIG. 31 perform the same functions as the terminal device 2, the network 3, and the servers 40a and 40b shown in FIG. . The transfer devices 30f and 30g perform the same functions as the transfer device 30e, and a description thereof will be omitted. Further, the server 40c is assumed to exhibit the same function as the server 40a or the server 40b, and the description thereof is omitted.

  The transfer device 30e stores, for each interface, whether or not the LAN to be connected has a gateway. Then, the transfer device 30e determines whether or not the interface that transmits the frame in which the IP packet is stored is connected to a LAN other than the LAN 11a, that is, the LAN 11b or the transfer devices 30f and 30g of the LAN 11c.

  Further, the transfer device 30e determines whether or not the LAN connected to the interface that transmits the frame in which the IP packet is stored is a LAN having a gateway, that is, the LAN 11b. Then, when the interface for sending the frame is connected to the transfer device 30f of the LAN 11b, the transfer device 30e determines whether the source IP address of the IP packet in the frame is within the network address range of the subnet 10. Determine whether or not. That is, the transfer device 30e determines whether or not the IP packet in the frame to be transmitted is an IP packet related to packet communication between the servers 40a to 40c that are internal devices of the subnet 10 and the terminal device 2 that is an external device of the subnet 10. Determine whether.

  Thereafter, when the transfer device 30e determines that the source IP address of the IP packet in the frame is not within the network address range of the subnet 10, the packet in the received frame using the packet in the received frame is It is determined that the packet is a roundabout packet. Then, the transfer device 30e notifies the terminal device 2 of the gateway switching via the gateway 20a.

  That is, in the example shown in FIG. 31, each of the LANs 11a and 11b has a gateway, but the LAN 11c does not have a gateway. For this reason, the IP packet in the frame transmitted from the transfer device 30e to the transfer device 30f is a candidate for a roundabout packet, but the IP packet in the frame transmitted to the transfer device 30g is not a candidate for a roundabout packet.

  Therefore, the transfer device 30e stores, for each interface, whether or not the LAN to be connected has a gateway. When the LAN that is the connection destination of the interface that sends out the frame in which the IP packet is stored has a gateway, the transfer device 30e determines that the IP packet in the frame to be sent is a roundabout packet candidate. Thereafter, like the transfer device 30a, the transfer device 30e determines whether or not the IP packet in the frame to be transmitted satisfies the detection rule. If the detection rule is satisfied, the packet in the frame is a roundabout packet. Is determined.

  In the example illustrated in FIG. 31, each transfer device 30e and 30f determines a roundabout packet, thereby preventing packet communication between the terminal device 2 and the server 40c from following the roundabout path. That is, when the terminal device 2 transmits an IP packet destined for the server 40c to the gateway 20b, the subnet 10 performs two LAN communication of the packet twice. However, when the transfer device 30f notifies the terminal device 2 of the gateway switching, the terminal device 2 transmits a frame in which an IP packet destined for the server 40c is stored to the gateway 20a. As a result, the transfer devices 30e and 30f can eliminate the roundabout path.

  Hereinafter, the functional configuration of the transfer device 30e will be described with reference to FIG. FIG. 32 is a schematic diagram illustrating an example of a functional configuration of the transfer apparatus according to the fifth embodiment. As illustrated in FIG. 32, the transfer device 30e includes an interface information storage unit 31a, a MAC learning table storage unit 32, and a roundabout packet identification information storage unit 33. The transfer device 30e includes a plurality of interfaces 34a to 34d, a plurality of transmission / reception units 35a to 35d, a message identification unit 36, a roundabout communication determination unit 37b, a route change notification unit 38, and a transfer processing unit 39. Here, the interface 34d is connected to the transfer device 30g.

  The MAC learning table storage unit 32 stores the information illustrated in FIG. 13 as in the first embodiment, and the roundabout packet identification information storage unit 33 stores the information illustrated in FIG. 14 as in the first embodiment. As an example, the description is omitted. Further, the interfaces 34a to 34d, the transmission / reception units 35a to 35d, the message identification unit 36, the path change notification unit 38, and the transfer processing unit 39 are omitted because they exhibit the same functions as those in the first embodiment.

  The interface information storage unit 31a stores interface information indicating whether the connection destination of each of the interfaces 34 to 34d is connected to a LAN other than the LAN 11a and whether a gateway exists in the connection destination LAN.

  FIG. 33 is a schematic diagram illustrating an example of interface information according to the fifth embodiment. As illustrated in FIG. 33, the interface information storage unit 31a stores an interface identifier, inter-LAN communication information, and gateway information of a connection destination LAN in association with each other. For example, the interface information storage unit 31a stores the inter-LAN communication information “No” in association with the interface identifier “IF # 1” indicating the interface 34a and the interface identifier “IF # 3” indicating the interface 34c. . The interface information storage unit 31a does not store the gateway information of the connection destination LAN when the inter-LAN communication information is “No”.

  Further, the interface information storage unit 31a stores an interface identifier “IF # 2” indicating the interface 34b, inter-LAN communication information “Yes”, and gateway information “Yes” of the connection destination LAN in association with each other. Further, the interface information storage unit 31a stores an interface identifier “IF # 4” indicating the interface 34d, the inter-LAN communication information “Yes”, and gateway information “none” of the connection destination LAN in association with each other.

  When the roundabout communication determination unit 37b receives a frame from the message identification unit 36, the roundabout communication determination unit 37b acquires the roundabout packet identification information stored in the roundabout packet identification information storage unit 33. Then, the roundabout communication determination unit 37b determines whether or not the packet in the received frame satisfies the detection rule of the roundabout packet identification information, the communication direction, and the communication content.

  Here, when the packet in the received frame satisfies the detection rule of the roundabout packet identification information, the communication direction, and the communication content, the roundabout communication determination unit 37b checks the interface information, and the destination LAN of the frame sets the gateway. It is determined whether or not it has. Then, the roundabout communication determination unit 37b outputs the packet in the received frame to the path change notification unit 38 when the frame destination LAN has a gateway. On the other hand, when the frame destination LAN does not have a gateway, the roundabout communication determination unit 37b discards the received frame.

  Hereinafter, an example of processing performed by the roundabout communication determination unit 37b will be described. In the following description, an example in which the interface information storage unit 31a stores the interface information illustrated in FIG. 33 and the roundabout packet identification information storage unit 33 stores the roundabout packet identification information illustrated in FIG. 14 will be described.

  For example, when the roundabout communication determination unit 37b receives the frame from the message identification unit 36, whether or not the transmission source IP address of the IP packet in the received frame is a value other than “192.168.0.0/24”. Determine whether. Further, when the source IP address of the IP packet in the frame is a value other than “192.168.0.0/24”, the roundabout communication determination unit 37b sets the communication direction of the roundabout packet identification information to “transmission”. Therefore, the destination MAC address of the received frame is identified. Next, the roundabout communication determination unit 37b reads the interface identifier of the output interface associated with the identified destination MAC address from the MAC learning table storage unit 32.

  Then, the roundabout communication determination unit 37b confirms the interface information stored in the interface information storage unit 31a, and determines whether or not the communication information between LANs associated with the read interface identifier is “Yes”. Thereafter, when the communication information between the LANs associated with the read interface identifier is “Yes”, the roundabout communication determination unit 37b has “Yes” for the gateway information of the connection destination LAN associated with the read interface identifier. It is determined whether or not.

  When the gateway information of the connection destination LAN associated with the read interface identifier is “Yes”, the roundabout communication determination unit 37b determines that the IP packet in the frame is a roundabout packet. On the other hand, the roundabout communication determination unit 37b determines that the transmission IP address of the IP packet in the frame is included in “192.168.0.0/24”, or the communication information between LANs of the interface that transmits the frame is “No. ", Discard the frame. The roundabout communication determination unit 37b discards the frame when the gateway information of the transmission destination LAN of the frame is “none”.

  For example, when the destination MAC address of the received frame is “M4”, the roundabout communication determination unit 37b reads the output interface “IF # 2” from the MAC learning table storage unit 32. Here, the roundabout communication determination unit 37b determines that the IP packet in the frame is a roundabout packet because the inter-LAN communication information of the output interface “IF # 2” is “Yes” and the gateway information is “Yes”. judge.

  On the other hand, when the destination MAC address of the received frame is “M5”, the roundabout communication determination unit 37b determines that the inter-LAN communication information of the output interface “IF # 4” is “Yes”. However, since the gateway information of the output interface “IF # 4” is “none”, the roundabout communication determination unit 37b determines that the IP packet in the frame is not a roundabout packet.

  That is, the transfer device 30e determines whether the IP packet in the frame is an IP packet related to packet communication between the inside of the subnet 10 and the terminal device 2 based on the transmission source IP address of the IP packet in the frame to be transmitted. Determine. Further, when the IP packet in the frame to be transmitted is an IP packet related to packet communication between the inside of the subnet 10 and the terminal device 2, the transfer device 30e determines whether the transmission destination of the frame is a LAN other than the LAN 11a. Determine.

  When the frame transmission destination is a LAN other than the LAN 11a, the transfer device 30e determines whether or not the LAN that is the frame transmission destination has a gateway. When the LAN that is the frame transmission destination has a gateway, the transfer device 30e determines that the IP packet in the frame to be transmitted is a roundabout packet.

  Therefore, the transfer device 30e can determine whether or not the packet in the received frame is a roundabout packet without managing the installation positions of the servers 40a to 40c included in the subnet 10. Also, the transfer device 30e determines whether or not the LAN that is the destination of the IP packet has a gateway. As a result, the transfer device 30e can eliminate the roundabout path even when the LAN having the gateway and the LAN not having the gateway are mixed in the subnet 10.

  Next, the flow of processing for determining whether or not the packet in the frame transmitted by the transfer device 30e to the transfer device 30f is a roundabout packet will be described with reference to FIG. FIG. 34 is a flowchart for explaining the flow of a roundabout packet determination process according to the fifth embodiment.

  First, when the transfer device 30e receives a frame from the gateway 20a, the transfer device 30f, or the server 40a (step S401), the transfer device 30e determines whether the type of the packet in the received frame is an IP packet (step S402). . Then, when the type of the packet in the received frame is an IP packet (Yes in step S402), the transfer device 30e determines whether or not the transmission source IP address of the IP packet in the received frame satisfies the detection rule. Determination is made (step S403).

  In addition, when the transmission source IP address of the IP packet in the received frame satisfies the detection rule (Yes in step S403), the transfer device 30e determines whether to transmit the received frame to the LAN 11b or the LAN 11c ( Step S404). When transmitting the received frame to the LAN 11b or LAN 11c (Yes at Step S404), the transfer device 30e determines whether or not there is a gateway in the LAN that is the transmission destination of the frame (Step S405). Thereafter, when there is a gateway in the LAN that is the frame transmission destination (Yes in step S405), the transfer device 30e determines that the packet in the received frame is a roundabout packet and transmits a roundabout notification message to the terminal device 2. (Step S406), and the process ends.

  On the other hand, when the type of the packet in the received frame is not an IP packet (No in step S402), the transfer device 30e determines that the packet in the received frame is not a roundabout packet (step S407), and performs processing. finish. Further, when the transmission source IP address of the IP packet in the received frame does not satisfy the detection rule (No in step S403), the transfer device 30e determines that the IP packet in the received frame is not a roundabout packet (step S407). ), The process is terminated. Even when the transfer device 30e does not transmit the received frame to the LAN 11b or the LAN 11c (No in step S404), the transfer device 30e determines that the packet in the received frame is not a roundabout packet (step S407), and ends the process. In addition, when there is no gateway in the destination LAN in the received frame (No in step S405), the transfer device 30e determines that the IP packet in the received frame is not a roundabout packet (step S407), and performs processing. finish.

[Effect of Example 5]
As described above, the transfer device 30e transfers a frame in which a packet is stored with the plurality of transfer devices 30f and 30g. Further, the transfer device 30e stores information indicating whether each interface is connected to a LAN other than the LAN 11a and information indicating whether the connection destination LAN has a gateway. When transmitting the frame to a LAN other than the LAN 11a, the transfer device 30e determines whether or not the LAN that is the transmission destination of the frame has a gateway. Thereafter, when the transfer device 30e determines that the LAN that is the transmission destination of the frame does not have a gateway, the transfer device 30e determines that the packet in the frame is not a roundabout packet.

  That is, the transfer device 30e determines that a packet in a frame addressed to the LAN 11c that is not directly connected to the network 3 is not a roundabout packet even if it is transferred beyond the LAN. As a result, the transfer device 30e can eliminate the roundabout path even when a LAN having a gateway and a LAN having no gateway are mixed in the subnet 10.

  In the sixth embodiment, a variation of the communication system 1b according to the fifth embodiment will be described. For example, the transfer device 30e determines a roundabout path using an IP packet in a frame transmitted to the transfer device 30f. However, the embodiment is not limited to this. For example, the transfer device 30f may determine the roundabout path using the IP packet in the frame received from the transfer device 30e.

  Hereinafter, processing for determining a roundabout path using an IP packet in a frame received by the transfer device 30f from the transfer device 30e will be described. For example, FIG. 35 is a schematic diagram illustrating variations of interface information according to the sixth embodiment. The transfer device 30f stores the interface identifier, the inter-LAN communication information, and the gateway IP address of the connection destination LAN in association with each other as interface information.

  Here, the interface identifier “IF # 4” is an identifier indicating an interface connected to the gateway 20b, and the interface identifier “IF # 5” is an identifier indicating an interface connected to the transfer device 30e. The interface identifier “IF # 6” is an identifier indicating an interface connected to the server 40b. Therefore, the transfer device 30f stores the interface identifiers “IF # 4” and “IF # 6” and the inter-LAN communication information “NO” in association with each other. Further, the transfer device 30f stores the interface identifier “IF # 5”, the inter-LAN communication information “YES”, and the gateway IP address “10.0.1.1” of the connection destination LAN in association with each other.

  FIG. 36 is a schematic diagram illustrating variations of roundabout packet identification information according to the sixth embodiment. For example, the transfer device 30f stores roundabout packet identification information illustrated in FIG. Specifically, the transfer device 30f has the target packet “IP packet”, the detection rule “source IP address ≠ 192.168.0.0 / 24”, communication direction “reception”, communication content “inter-LAN communication information” The roundabout packet identification information associated with “= Yes” is stored.

  Next, processing for determining whether or not a packet in the received frame is a roundabout packet will be described. For example, when the transfer device 30f receives a frame from any one of the gateway 20b, the server 40f, and the transfer device 30e, the target packet of the roundabout packet identification information is an “IP packet”, so that the packet in the received frame is an IP packet. It is determined whether or not. Further, when the packet in the received frame is an IP packet, the transfer device 30f determines whether or not the source IP address of the IP packet in the frame satisfies the detection rule of the roundabout packet identification information.

  Specifically, since the detection rule of the roundabout packet identification information is “source IP address ≠ 192.168.0.0 / 24”, the transfer device 30f has the source IP address of the IP packet in the frame “192”. It is determined whether the value is other than “.168.0.0 / 24”. When the transmission source IP address of the IP packet in the frame is a value other than “192.168.0.0/24”, the transfer device 30f indicates that the communication information between the LANs of the interface that received the frame is “Yes”. Is determined.

  As a result, if the inter-LAN communication information of the interface that received the frame is “Yes”, the transfer device 30f determines that the IP packet in the received frame is a roundabout packet. For example, when the interface identifier of the interface that has received the frame is “IF # 5”, the transfer device 30f indicates that the IP packet in the received frame is roundabout because the inter-LAN communication information in the interface information is “Yes”. Judged to be a packet.

  When the IP packet in the received frame is a roundabout packet, the transfer device 30f acquires the IP address of the gateway associated with the interface identifier of the interface that has received the frame. For example, when the interface identifier of the interface that received the frame is “IF # 5”, the transfer device 30f acquires the IP address “10.0.1.1” of the gateway 20a. Then, the transfer device 30f transmits a roundabout notification message including the acquired IP address.

  As described above, when the roundabout packet is detected using the source IP address of the IP packet in the frame received by the transfer device 30f, the transfer device 30g is set not to detect the roundabout packet. . On the other hand, as with the transfer device 30f, the transfer device 30e may detect a roundabout packet using the source IP address of the IP packet in the received frame.

  Further, the transfer device 30f may detect a roundabout packet using the ARP response in the frame, similarly to the transfer device 30c. For example, FIG. 37 is a diagram illustrating a variation in the functional configuration of the transfer apparatus according to the sixth embodiment. As illustrated in FIG. 37, the transfer device 30f includes an interface information storage unit 31, a MAC learning table storage unit 32, and a roundabout packet identification information storage unit 33b.

  The transfer device 30f includes a plurality of interfaces 34a to 34c, a plurality of transmission / reception units 35a to 35c, a message identification unit 36, a roundabout communication determination unit 37b, a MAC address list storage unit 37c, a route change notification unit 38, and a transfer processing unit 39. Have Note that the interface information storage unit 31 and the MAC learning table storage unit 32 store the same information as in the first embodiment, and a description thereof will be omitted. Further, the interfaces 34a to 34c, the transmission / reception units 35a to 35c, the message identification unit 36, the route change notification unit 38, and the transfer processing unit 39 are omitted because they exhibit the same functions as those in the first embodiment.

  The MAC address list storage unit 37c stores the MAC addresses of all gateways included in the subnet 10. For example, FIG. 38 is a diagram for explaining an example of the MAC address list of the gateway. As illustrated in FIG. 38, the MAC address list storage unit 37c stores a MAC address list in which the MAC address “M1” of the gateway 20a and the MAC address “M4” of the gateway 20b are stored.

  Returning to FIG. 37, the roundabout packet identification information storage unit 33b stores roundabout packet identification information that is a rule for determining whether or not the packet transmitted and received by the transfer device 30f is a roundabout packet. For example, FIG. 39 is a diagram for explaining a variation of roundabout packet identification information when a roundabout packet is determined using an ARP response.

  In the example shown in FIG. 39, the roundabout packet identification information storage unit 33b performs “ARP response” as the target packet, “destination MAC address = MAC address list” as the detection rule, “send” as the communication direction, and “between LANs” as the communication content. “Communication information = Yes” is stored. Therefore, when the ARP response whose destination MAC address matches one of the MAC address lists is stored in the frame transmitted to the LAN other than the LAN 10b, the transfer device 30f uses the roundabout packet as the ARP response in the frame. It is determined that

  Hereinafter, an example of processing performed by the roundabout communication determination unit 37b will be described. For example, since the target packet of the roundabout packet identification information is an “ARP response”, the roundabout communication determination unit 37b determines whether the packet in the received frame is an ARP response. Here, the detection rule of the roundabout packet identification information is “destination MAC address = MAC address list”. For this reason, when the packet in the received frame is an ARP response, the roundabout communication determination unit 37b determines whether the destination MAC address of the ARP response in the frame matches one of the MAC address lists.

  Further, since the communication direction of the roundabout packet identification information is “transmission”, the roundabout communication determination unit 37b identifies the interface that transmits the frame from the destination MAC address. Then, the roundabout communication determination unit 37b confirms the interface information, and determines whether or not the communication information between LANs associated with the interface identifier of the identified interface is “Yes”.

  When the communication information between LANs associated with the interface identifier of the identified interface is “Yes”, the roundabout communication determination unit 37b determines that the ARP response in the frame is a roundabout packet. Then, the roundabout communication determination unit 37b transmits a roundabout notification message to the gateway indicated by the destination MAC address of the ARP response in the frame.

[Effect of Example 6]
As described above, the transfer device 30f stores information indicating whether each interface is connected to a LAN other than the LAN 11a and the MAC addresses of the gateways 20a and 20b included in the subnet 10. When the destination MAC address of the ARP response in the frame to be transmitted to the LAN 11a matches the MAC address of either the gateway 20a or the gateway 20b, the transfer device 30f has a roundabout path as the packet communication path. Is determined.

  For this reason, the transfer device 30 f can notify the switching of the gateway before the IP packet via the bypass route flows to the subnet 10. In addition, the communication system 1b is set so that the LAN transfer device having the gateway, for example, the transfer device 30e performs the same function as the transfer device 30f, and the LAN transfer device without the gateway determines the roundabout packet. Set to not. As a result, the communication system 1b can prevent packet communication via a roundabout path even when a LAN having a gateway and a LAN having no gateway are mixed in the subnet 10.

  Although the embodiments of the present invention have been described so far, the embodiments may be implemented in various different forms other than the embodiments described above. Accordingly, another embodiment included in the present invention will be described below as a seventh embodiment.

(1) Communication System In the communication systems 1 and 1a described above, the transfer apparatuses 30a to 30d connect the first base 4 and the second base 5 to each other. However, the embodiment is not limited to this. For example, the communication systems 1 and 1a may connect three or more bases. Here, the communication systems 1 and 1a may connect three or more bases in stages, or may connect in cascade. Further, the first base 4 and the second base 5 may have two or more LANs, and each LAN may be connected by a transfer device. That is, the communication system 1, 1a, 1b may have a subnet 10 to which an arbitrary number of LANs are connected.

  Further, the terminal device 2 is not limited to the information processing device that receives the provision of various services, and may be, for example, an access gateway installed in a network different from the network 3 and the subnet 10. Moreover, the connection form of each LAN 11a-11c shown to each communication system 1, 1a, 1b mentioned above is not limited to an Example, For example, you may connect in a ring shape or each mutually A connected connection form may be used.

(2) Processing of each transfer device For example, the transfer device 30a and the transfer device 30b can perform a process of simultaneously detecting a roundabout packet using the same roundabout packet identification information. The transfer device 30a and the transfer device 30b can also use different roundabout packet identification information. The setting of roundabout packet identification information is not limited to the above-described example.

  For example, each of the transfer devices 30a to 30g can use arbitrary roundabout packet identification information whose parameters are the connection form of the LAN included in the subnet 10, the presence / absence of a gateway, the type of packet used for roundabout packet detection, and the like. For example, each of the transfer devices 30a to 30g may determine a roundabout packet based on any of the destination IP address, the destination MAC address, the source IP address, or the destination IP address of the packet stored in the frame to be transferred. .

  Further, the roundabout packet identification information stored in the transfer devices 30a to 30g described above is not limited to the contents described in the above description. In other words, each of the transfer devices 30a to 30g, when the packet in the frame transmitted / received between LANs having gateways is a packet related to packet communication between the inside of the subnet 10 and the outside of the subnet 10, It may be determined to be interposed.

(3) Functional configuration Of the processes described above, all or part of the processes described as being automatically performed can be manually performed. Alternatively, all or part of the processing described as being performed manually can be automatically performed by a known method. In addition, the processing procedures, specific names, and information including various data and parameters shown in the document and drawings can be arbitrarily changed unless otherwise specified.

  Further, each component of each illustrated apparatus is functionally conceptual, and does not necessarily need to be physically configured as illustrated. That is, the specific form of distribution and integration of each device is not limited to the illustrated one. That is, all or a part of them can be configured to be functionally or physically distributed / integrated in arbitrary units according to various loads or usage conditions. Further, all or any part of each processing function performed in each device may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic.

(4) Program Various processes described in the above embodiments can be realized by executing a program prepared in advance on a computer such as a personal computer or a workstation. Therefore, an example of a computer that executes a determination program having the same function as that of the transfer device 30a will be described below with reference to FIG.

  FIG. 40 is a diagram for describing an example of a computer that executes a determination program. As shown in FIG. 40, the computer 100 includes an HDD (Hard Disk Drive) 150, a ROM (Read Only Memory) 160, a RAM (Random Access Memory) 170, a CPU (Central Processing Unit) 180, an I / O (I / O). Input / Output) 190. These units 150 to 190 are connected via a bus 140. Here, the computer 100 is a microprocessor or the like included in a transfer device such as an L3 switch.

  In the RAM 170, a determination program 170a for causing the CPU 180 to perform the function of the transfer device 30a, interface information 170b, roundabout packet identification information 170c, and a MAC learning table 170d are stored in advance. The determination program 170a may be appropriately integrated or separated as in the case of each component shown in the first embodiment.

  The determination program 170a functions as the determination process 180a when the CPU 180 reads out, expands and executes the determination program 170a. The determination process 180a executes various processes based on the interface information 170b, the roundabout packet identification information 170c, and the MAC learning table 170d read from the RAM 170.

  The CPU 180 that has executed the determination process 180 a executes the same processing as the message identification unit 36, the roundabout communication determination unit 37, the route change notification unit 38, and the transfer processing unit 39. In addition, each processing virtually realized on the CPU 180 does not always require that all processing units operate on the CPU 180, and only the processing necessary for the processing needs to be virtually realized.

  Note that the determination program 170a is not necessarily stored in the RAM 170 from the beginning. For example, each of the “portable physical media” such as a flexible disk inserted into the computer 100, so-called FD (Flexible Disk), CD (Compact Disk) -ROM, DVD (Digital Video Disk), magneto-optical disk, IC card, etc. Remember the program.

  Then, the computer 100 may acquire and execute each program from these portable physical media. The computer 100 may acquire and execute each program stored in another computer or a server device via a public line, the Internet, a LAN, a WAN (Wide Area Network), or the like.

  In addition to the determination program 170a, the computer 100 illustrated in FIG. 40 can execute, for example, a determination program having the same function as each of the transfer devices 30a to 30g.

  The following supplementary notes are further disclosed with respect to the embodiments including the above examples.

(Appendix 1) A transfer device installed in a unit network having a gateway,
A transmission / reception unit for transmitting / receiving a frame to / from a transfer device installed in another unit network in the network including the unit network;
Based on the destination address or source address of the packet in the frame transmitted and received by the transceiver, the packet relates to communication between the internal device installed in the network and the external device installed outside the network A determination unit for determining whether the packet is a packet;
And a notification unit that notifies the external device of a gateway switching instruction when the determination unit determines that the packet is a packet related to communication between the internal device and the external device. Transfer device.

(Supplementary Note 2) The determination unit is a transmission source IP address of an IP (Internet Protocol) packet in a frame transmitted by the transmission / reception unit, a destination IP address of an IP packet in a frame received by the transmission / reception unit, or the transmission / reception When the source IP address of the IP packet in the frame received by the unit is an address other than the network address assigned to the network, the IP packet is an IP packet related to communication between the internal device and the external device. The transfer device according to appendix 1, wherein the transfer device is determined to be present.

(Supplementary Note 3) When the determination unit determines that the IP packet is an IP packet related to communication between the internal device and the external device, the notification unit, or a source IP address of the IP packet, The transfer device according to appendix 2, wherein the gateway switching instruction is notified to the external device indicated by the destination IP address of the IP packet.

(Additional remark 4) The said notification part instruct | indicates the said external apparatus to switch the gateway at the time of transmitting an IP packet to the said internal apparatus which the destination IP address of the said IP packet or the transmission source IP address of the said IP packet shows 4. The transfer device according to appendix 2 or 3, wherein a switching instruction is sent.

(Additional remark 5) When the determination part is the MAC (Media Access Control address) address of the gateway installed in the unit network, the destination MAC address of the ARP (Address Resolution Protocol) response in the frame received by the transceiver The transfer device according to appendix 1, wherein the ARP response is determined to be a packet related to communication between the internal device and the external device.

(Additional remark 6) It has a MAC address memory | storage part which memorize | stores the MAC address of the gateway installed in the said network,
When the destination MAC address of the ARP response in the frame transmitted by the transmission / reception unit matches one of the MAC addresses stored in the MAC address storage unit, the determination unit determines that the ARP response is transmitted between the internal device and the external device. The transfer apparatus according to appendix 1, wherein the transfer apparatus determines that the packet is related to communication with the apparatus.

(Supplementary Note 7) When the determination unit determines that the ARP response is a packet related to communication between the internal device and the external device, the notification unit sends a message to the gateway to which the destination MAC address of the ARP response is assigned. The transfer device according to appendix 5 or 6, wherein the transfer device is instructed to transmit the switching instruction to the external device.

(Additional remark 8) The said notification part notifies the switching instruction | indication which instruct | indicates to switch the gateway at the time of transmitting an IP packet to the said internal device which the IP address which shows the transmission origin of the said ARP response with respect to the said external device The transfer device according to any one of appendices 5 to 7, characterized in that:

(Supplementary note 9) one or a plurality of the transceiver units;
Gateway information for storing the gateway information indicating whether or not a gateway is installed in the other unit network and the identifier of the transmission / reception unit that transmits / receives a frame to / from the transfer device installed in the other unit network A storage unit;
The determination unit determines whether or not a packet in the frame is a packet related to communication between the internal device and the external device, and an identifier of the transmission / reception unit that transmits / receives the packet and the gateway information storage unit and the gateway Is stored in association with gateway information indicating that is installed,
The notifying unit indicates that the packet is a packet related to communication between the internal device and the external device, and that the gateway information storage unit transmits and receives the packet and the identifier of the transmitting / receiving unit and the gateway are installed. Any one of appendixes 1 to 8, wherein when the determining unit determines that the gateway information indicating the gateway is stored in association with the gateway information, the external device is notified of a gateway switching instruction. The transfer device described in 1.

(Supplementary Note 10) One or a plurality of the transmission / reception units, an IP address of a gateway installed in the other unit network, and an identifier of the transmission / reception unit that transmits / receives a frame to / from a transfer device installed in the other network Having an address storage unit for storing in association with each other;
The determination unit is a communication between the internal device and the external device based on a destination address or a source address of a packet in a frame transmitted and received by the transmission / reception unit, and is installed in the unit network. To determine whether the packet is related to communication via the gateway,
The notification unit, when the determination unit determines that the packet is communication between the internal device and the external device, and is a packet related to communication via a gateway installed in the unit network, Appendices 1 to 9, wherein the address storage unit acquires an IP address of a gateway stored in association with an identifier of a transmission / reception unit that has transmitted and received the packet, and notifies the acquired IP address and a gateway switching instruction The transfer device according to any one of the above.

(Additional remark 11) The said determination part is communication between the said internal apparatus and the said external apparatus based on the destination address or transmission source address of the packet in the flame | frame which the said transmission / reception part transmits / receives, and the said unit Determine whether the packet is for communication via a gateway installed in the network,
The notification unit determines that the packet is communication between the internal device and the external device, and is a packet related to communication via a gateway installed in the unit network, and the determination unit Any one of appendixes 1 to 10, wherein a gateway switching instruction is notified to the external device when a gateway installed in the other unit network as a packet transmission / reception destination is not faulty. Transfer device described in one.

(Supplementary Note 12) A gateway that relays a frame related to communication between an internal device installed in a network including a plurality of unit networks and an external device installed outside the network;
In a communication system having a transfer device installed in the unit network in which the gateway is installed,
The transfer device is
A transmission / reception unit for transmitting / receiving a frame to / from a transfer device installed in another unit network in the network;
A determination unit that determines whether the packet is a packet related to communication between the internal device and the external device based on a destination address or a source address of a packet in a frame transmitted and received by the transmission / reception unit; ,
When the determination unit determines that the packet is a packet related to communication between the internal device and the external device, a notification unit that notifies the gateway that the transfer route of the packet is roundabout; Have
The gateway is
A switching instruction unit that instructs the transfer device that is a transmission source of the packet to switch the gateway when receiving a notification from the notification unit that the transfer path of the packet is roundabout. Communication system.

(Supplementary Note 13) The gateway stores a destination IP address and a source IP address of an IP (Internet Protocol) packet received from the external device in association with each other,
An ARP (Address Resolution Protocol) request that uses a destination IP address of an IP packet received from the external device as a target address), and
When the destination MAC (Media Access Control address) address of the ARP response in the frame received by the transmission / reception unit is the MAC address of the gateway installed in the unit network, the determination unit determines that the ARP response is the internal device And a packet related to communication with the external device,
When the determination unit determines that the ARP response is a packet related to communication between the internal device and the external device, the notification unit sends a transmission source protocol address stored in the ARP response to the gateway. , Notify that the transfer path of the packet is roundabout,
The switching instruction unit associates the source protocol address with the destination address that matches the source protocol address when receiving a notification from the notification unit that the packet transfer path is roundabout. 13. The communication system according to appendix 12, wherein the external device indicated by the transmitted source IP address is instructed to switch the gateway.

(Supplementary note 14)
Corresponds to the IP address of the internal device that is the source of the ARP response, the MAC address of the internal device, and detour information indicating whether or not the transfer path of the packet from the gateway to the internal device is detoured A detour information storage unit for storing information;
When the notification that the transfer route of the packet is roundabout is received from the notification unit, the roundabout information stored in the roundabout information storage unit in association with the destination IP address of the packet is the roundabout transfer route An update unit for updating to detour information;
When receiving an IP packet from the external device, the determination unit determines whether or not the roundabout information storage unit stores the roundabout information indicating that the transfer route is roundabout in association with the destination IP address of the IP packet. When,
When the determination unit determines that the roundabout information storage unit stores the roundabout information in which the transfer route is roundabout in association with the destination IP address of the IP packet, 14. The communication system according to appendix 13, wherein the external device that is the source of the IP packet is instructed to switch the gateway.

(Additional remark 15) In the roundabout path detection method which the transfer apparatus installed in the unit network which has a gateway performs,
Sending and receiving frames to and from transfer devices installed in other unit networks in the network including the unit network,
Whether the packet is a packet related to communication between an internal device installed in the network and an external device installed outside the network based on the destination address or the source address of the packet in the frame Determine whether
When it is determined that the packet is a packet related to communication between the internal device and the external device, a process for notifying the external device of a gateway switching instruction is executed. .

(Supplementary Note 16) The source IP address of an IP (Internet Protocol) packet in a frame to be transmitted, the destination IP address of an IP packet in a received frame, or the source IP address of an IP packet in a received frame is the network 16. The roundabout path detection according to appendix 15, wherein the IP packet is determined to be an IP packet related to communication between the internal device and the external device when the address is other than the network address assigned to Method.

(Supplementary Note 17) When it is determined that the IP packet is an IP packet related to communication between the internal device and the external device, the source IP address of the IP packet or the destination IP address of the IP packet indicates The roundabout path detection method according to appendix 16, wherein an instruction to switch the gateway is sent to an external device.

(Supplementary Note 18) Notification of a switching instruction for instructing the external device to switch the gateway for transmitting the IP packet to the internal device indicated by the destination IP address of the IP packet or the source IP address of the IP packet 18. The roundabout path detection method according to appendix 16 or 17, characterized in that:

(Supplementary note 19) When the destination MAC (Media Access Control address) address of the ARP (Address Resolution Protocol) response in the received frame is the MAC address of the gateway installed in the unit network, the ARP response is the internal device The roundabout path detection method according to claim 15, wherein the packet is determined to be a packet related to communication with the external device.

(Supplementary note 20) When the destination MAC address of the ARP response to be transmitted is stored in the MAC address storage unit that stores the MAC address of the gateway installed in the network, the ARP response is transmitted between the internal device and the external device. 16. The roundabout path detection method according to appendix 15, wherein the packet is determined to be a packet related to communication with the network.

(Supplementary Note 21) When it is determined that the ARP response is a packet related to communication between the internal device and the external device, the switching instruction is sent to the gateway to which the destination MAC address of the ARP response is assigned. The roundabout path detection method according to appendix 19 or 20, characterized in that an instruction is sent to the apparatus.

(Supplementary Note 22) A switch instruction for notifying the external device to switch the gateway when transmitting an IP packet to the internal device indicated by the IP address indicating the transmission source of the ARP response is sent to the external device. The roundabout path detection method according to any one of 19 to 21.

(Supplementary Note 23) A packet relating to communication between the internal device and the external device, and gateway information indicating whether a gateway is installed in the other unit network, and installed in the other unit network The gateway information storage unit that stores the transfer device and the identifier of the interface that transmits and receives frames in association with each other associates the identifier of the transmission and reception unit that transmits and receives the packet with the gateway information indicating that the gateway is installed. The roundabout path detection method according to any one of supplementary notes 15 to 22, wherein if it is determined that the information is stored, a gateway switching instruction is notified to the external device.

(Supplementary Note 24) Based on the destination address or transmission source address of the packet in the frame to be transmitted / received, the packet is communication between the internal device and the external device, and passes through the gateway installed in the unit network. Determine whether the packet is for communication,
If the packet is communication between the internal device and the external device and is determined to be a packet related to communication via the gateway installed in the unit network, the gateway installed in the other unit network Is stored in association with the identifier of the interface that has transmitted and received the packet, the address storage unit that stores the IP address of the interface and the identifier of the interface that transmits and receives the packet in association with the transfer device installed in the other network 24. The roundabout path detection method according to any one of appendices 15 to 23, wherein the IP address is acquired, and the acquired IP address and a gateway switching instruction are notified.

(Supplementary Note 25) Based on a destination address or a source address of a packet in the frame, the packet is communication between the internal device and the external device, and communication is performed via a gateway installed in the unit network. Whether the packet is related to
The packet is communication between the internal device and the external device, and is determined to be a packet related to communication via a gateway installed in the unit network, and the other packet that is a transmission / reception destination of the packet 25. The roundabout path detection method according to any one of appendices 15 to 24, wherein when the gateway installed in the unit network is not out of order, the external apparatus is notified of a gateway switching instruction.

1, 1a, 1b Communication system 2 Terminal device 3 Network 3a Router 4 First base 5 Second base 6 Third base 10 Subnet 11a to 11c LAN
12a Routing table 12b ARP cache table 13 Data generation unit 14 Transfer processing unit 17 Message identification unit 18 Data processing unit 19 Routing table update unit 20a to 20d Gateway 16, 21, 28, 34a to 34d Interfaces 15, 22, 27, 35a to 35d Transmission / reception unit 23 Message identification unit 24, 24a Roundabout communication identification unit 25, 25a Route change notification unit 26, 26a Transfer processing unit 29a ARP cache table storage unit 29b Address correspondence table storage unit 30a-30g Transfer device 31, 31a Interface information storage Unit 32 MAC learning table storage unit 33, 33a, 33b roundabout packet identification information storage unit 36 message identification unit 37, 37a, 37b roundabout communication determination unit 37c MAC address list憶部 38 path change notifying unit 39 transfer processing unit 40a~40c server

Claims (15)

A transfer device installed in a unit network having a gateway,
A transmission / reception unit for transmitting / receiving a frame to / from a transfer device installed in another unit network in the network including the unit network;
Based on the destination address or source address of the packet in the frame transmitted and received by the transceiver, the packet relates to communication between the internal device installed in the network and the external device installed outside the network A determination unit for determining whether the packet is a packet;
And a notification unit that notifies the external device of a gateway switching instruction when the determination unit determines that the packet is a packet related to communication between the internal device and the external device. Transfer device.   The determination unit is a transmission source IP address of an IP (Internet Protocol) packet in a frame transmitted by the transmission / reception unit, or a destination IP address of an IP packet in a frame received by the transmission / reception unit, or received by the transmission / reception unit If the source IP address of the IP packet in the frame is an address other than the network address assigned to the network, it is determined that the IP packet is an IP packet related to communication between the internal device and the external device The transfer apparatus according to claim 1.   The notification unit, when the determination unit determines that the IP packet is an IP packet related to communication between the internal device and the external device, a source IP address of the IP packet, or a destination of the IP packet The transfer apparatus according to claim 2, wherein an instruction to switch the gateway is notified to the external apparatus indicated by an IP address.   The notification unit issues a switching instruction to instruct the external device to switch a gateway when transmitting an IP packet to the internal device indicated by a destination IP address of the IP packet or a source IP address of the IP packet. The transfer device according to claim 2 or 3, wherein notification is performed.   If the destination MAC (Media Access Control address) address of the ARP (Address Resolution Protocol) response in the frame received by the transmission / reception unit is the MAC address of the gateway installed in the unit network, the determination unit The transfer apparatus according to claim 1, wherein the response is determined to be a packet related to communication between the internal apparatus and the external apparatus. A MAC address storage unit for storing a MAC address of a gateway installed in the network;
When the destination MAC address of the ARP response in the frame transmitted by the transmission / reception unit matches one of the MAC addresses stored in the MAC address storage unit, the determination unit determines that the ARP response is transmitted between the internal device and the external device. The transfer apparatus according to claim 1, wherein the transfer apparatus determines that the packet is related to communication with the apparatus.   When the determination unit determines that the ARP response is a packet related to communication between the internal device and the external device, the notification unit performs the switching to the gateway to which the destination MAC address of the ARP response is assigned. The transfer apparatus according to claim 5, wherein the transfer apparatus instructs to transmit the instruction to the external apparatus.   The notification unit notifies the external device of a switching instruction instructing to switch a gateway when transmitting an IP packet to the internal device indicated by an IP address indicating a transmission source of the ARP response. The transfer device according to claim 5. One or more of said transceiver units;
Gateway information for storing the gateway information indicating whether or not a gateway is installed in the other unit network and the identifier of the transmission / reception unit that transmits / receives a frame to / from the transfer device installed in the other unit network A storage unit;
The determination unit determines whether or not a packet in the frame is a packet related to communication between the internal device and the external device, and an identifier of the transmission / reception unit that transmits / receives the packet and the gateway information storage unit and the gateway Is stored in association with gateway information indicating that is installed,
The notifying unit indicates that the packet is a packet related to communication between the internal device and the external device, and that the gateway information storage unit transmits and receives the packet and the identifier of the transmitting / receiving unit and the gateway are installed. The gateway switching instruction is notified to the external device when the determination unit determines that the gateway information indicating the gateway is stored in association with the gateway information. Transfer device described in one. One or a plurality of the transmission / reception units, an IP address of a gateway installed in the other unit network, and an identifier of the transmission / reception unit that transmits / receives a frame to / from a transfer device installed in the other network are stored in association with each other. An address storage unit
The determination unit is a communication between the internal device and the external device based on a destination address or a source address of a packet in a frame transmitted and received by the transmission / reception unit, and is installed in the unit network. To determine whether the packet is related to communication via the gateway,
The notification unit, when the determination unit determines that the packet is communication between the internal device and the external device, and is a packet related to communication via a gateway installed in the unit network, The address storage unit acquires an IP address of a gateway stored in association with an identifier of a transmission / reception unit that has transmitted and received the packet, and notifies the acquired IP address and a gateway switching instruction. The transfer device according to any one of 9. The determination unit is a communication between the internal device and the external device based on a destination address or a source address of a packet in a frame transmitted and received by the transmission / reception unit, and is installed in the unit network. To determine whether the packet is related to communication via the gateway,
The notification unit determines that the packet is communication between the internal device and the external device, and is a packet related to communication via a gateway installed in the unit network, and the determination unit 11. The gateway switching instruction is notified to the external device when a gateway installed in the other unit network that is a packet transmission / reception destination is not faulty. The transfer device according to one. A gateway that relays a frame related to communication between an internal device installed in a network including a plurality of unit networks and an external device installed outside the network;
In a communication system having a transfer device installed in the unit network in which the gateway is installed,
The transfer device is
A transmission / reception unit for transmitting / receiving a frame to / from a transfer device installed in another unit network in the network;
A determination unit that determines whether the packet is a packet related to communication between the internal device and the external device, based on a destination address of a packet in a frame transmitted and received by the transmission / reception unit, or a transmission source address;
When the determination unit determines that the packet is a packet related to communication between the internal device and the external device, a notification unit that notifies the gateway that the transfer route of the packet is roundabout; Have
The gateway is
A switching instruction unit that instructs the transfer device that is a transmission source of the packet to switch the gateway when receiving a notification from the notification unit that the transfer path of the packet is roundabout. Communication system. The gateway stores a destination IP address and a source IP address of an IP (Internet Protocol) packet received from the external device in association with each other;
A request transmission unit that transmits an ARP (Address Resolution Protocol) request using a destination IP address of an IP packet received from the external device as a target address;
Have
When the destination MAC (Media Access Control address) address of the ARP response in the frame received by the transmission / reception unit is the MAC address of the gateway installed in the unit network, the determination unit determines that the ARP response is the internal device And a packet related to communication with the external device,
When the determination unit determines that the ARP response is a packet related to communication between the internal device and the external device, the notification unit sends a transmission source protocol address stored in the ARP response to the gateway. , Notify that the transfer path of the packet is roundabout,
The switching instruction unit associates the source protocol address with the destination address that matches the source protocol address when receiving a notification from the notification unit that the packet transfer path is roundabout. The communication system according to claim 12, wherein the external device indicated by the transmitted source IP address is instructed to switch the gateway. The gateway is
Corresponds to the IP address of the internal device that is the source of the ARP response, the MAC address of the internal device, and detour information indicating whether or not the transfer path of the packet from the gateway to the internal device is detoured A detour information storage unit for storing information;
When the notification that the transfer route of the packet is roundabout is received from the notification unit, the roundabout information stored in the roundabout information storage unit in association with the destination IP address of the packet is the roundabout transfer route An update unit for updating to detour information;
When receiving an IP packet from the external device, the determination unit determines whether or not the roundabout information storage unit stores the roundabout information indicating that the transfer route is roundabout in association with the destination IP address of the IP packet. When,
When the determination unit determines that the roundabout information storage unit stores the roundabout information in which the transfer route is roundabout in association with the destination IP address of the IP packet, The communication system according to claim 13, wherein an instruction is given to switch an gateway to an external device that is a transmission source of an IP packet. In a roundabout path detection method executed by a transfer device installed in a unit network having a gateway,
Sending and receiving frames to and from transfer devices installed in other unit networks in the network including the unit network,
Whether the packet is a packet related to communication between an internal device installed in the network and an external device installed outside the network based on the destination address or the source address of the packet in the frame Determine whether
When it is determined that the packet is a packet related to communication between the internal device and the external device, a process for notifying the external device of a gateway switching instruction is executed. .

Images